diff --git a/fastdeploy/engine/common_engine.py b/fastdeploy/engine/common_engine.py
index 72ca1f7c820..39379c62c64 100644
--- a/fastdeploy/engine/common_engine.py
+++ b/fastdeploy/engine/common_engine.py
@@ -65,6 +65,10 @@
 )
 from fastdeploy.inter_communicator.fmq import FMQ
 from fastdeploy.metrics.metrics import main_process_metrics
+from fastdeploy.metrics.prometheus_multiprocess_setup import (
+    get_original_prom_dir,
+    setup_dp_prometheus_dir,
+)
 from fastdeploy.model_executor.guided_decoding import schema_checker
 from fastdeploy.plugins.token_processor import load_token_processor_plugins
 from fastdeploy.spec_decode import SpecMethod
@@ -2720,6 +2724,7 @@ def launch_components(self):
                 self.launched_expert_service_signal.value[0] = 1
                 self.dp_processed = []
                 self.dp_engine_worker_queue_server = []
+                base_prom_dir = get_original_prom_dir()
                 for i in range(
                     1,
                     self.cfg.parallel_config.data_parallel_size // self.cfg.nnode,
@@ -2758,10 +2763,15 @@ def launch_components(self):
                         f"Engine is initialized successfully with {self.cfg.parallel_config.tensor_parallel_size}"
                         + f" data parallel id {i}"
                     )
+                    if envs.FD_ENABLE_INTERNAL_ADAPTER:
+                        setup_dp_prometheus_dir(i, base_prom_dir)
                     self.dp_processed[-1].start()
                     while self.launched_expert_service_signal.value[i] == 0:
                         time.sleep(1)
 
+                if envs.FD_ENABLE_INTERNAL_ADAPTER:
+                    setup_dp_prometheus_dir(0, base_prom_dir)
+
     def check_worker_initialize_status(self):
         """
         Check the initlialize status of workers by stdout logging
diff --git a/fastdeploy/engine/engine.py b/fastdeploy/engine/engine.py
index 8614d29999b..ad71506d0f2 100644
--- a/fastdeploy/engine/engine.py
+++ b/fastdeploy/engine/engine.py
@@ -50,6 +50,10 @@
     log_request_error,
 )
 from fastdeploy.metrics.metrics import main_process_metrics
+from fastdeploy.metrics.prometheus_multiprocess_setup import (
+    get_original_prom_dir,
+    setup_dp_prometheus_dir,
+)
 from fastdeploy.platforms import current_platform
 from fastdeploy.utils import EngineError, console_logger, envs, llm_logger
 
@@ -860,6 +864,7 @@ def launch_components(self):
                 self.launched_expert_service_signal.value[0] = 1
                 self.dp_processed = []
                 self.dp_engine_worker_queue_server = []
+                base_prom_dir = get_original_prom_dir()
                 for i in range(
                     1,
                     self.cfg.parallel_config.data_parallel_size // self.cfg.nnode,
@@ -897,8 +902,13 @@ def launch_components(self):
                         f"Engine is initialized successfully with {self.cfg.parallel_config.tensor_parallel_size}"
                         + f" data parallel id {i}"
                     )
+                    if envs.FD_ENABLE_INTERNAL_ADAPTER:
+                        setup_dp_prometheus_dir(i, base_prom_dir)
                     self.dp_processed[-1].start()
 
+                if envs.FD_ENABLE_INTERNAL_ADAPTER:
+                    setup_dp_prometheus_dir(0, base_prom_dir)
+
                 for i in range(
                     1,
                     self.cfg.parallel_config.data_parallel_size // self.cfg.nnode,
diff --git a/fastdeploy/entrypoints/openai/multi_api_server.py b/fastdeploy/entrypoints/openai/multi_api_server.py
index 545fe2b1fb1..dbef909bf2c 100644
--- a/fastdeploy/entrypoints/openai/multi_api_server.py
+++ b/fastdeploy/entrypoints/openai/multi_api_server.py
@@ -20,6 +20,7 @@
 import sys
 import time
 
+from fastdeploy.metrics.prometheus_multiprocess_setup import setup_dp_prometheus_dir
 from fastdeploy.platforms import current_platform
 from fastdeploy.utils import find_free_ports, get_logger, is_port_available
 
@@ -108,13 +109,7 @@ def start_servers(
         env["FD_ENABLE_MULTI_API_SERVER"] = "1"
         env["FD_LOG_DIR"] = env.get("FD_LOG_DIR", "log") + f"/log_{i}"
         if "PROMETHEUS_MULTIPROC_DIR" in env:
-            prom_dir = env.get("PROMETHEUS_MULTIPROC_DIR")
-            prom_dir_i = os.path.join(os.path.dirname(prom_dir), os.path.basename(prom_dir) + f"_dp{i}")
-            # Create the directory if it doesn't exist
-            if not os.path.exists(prom_dir_i):
-                os.makedirs(prom_dir_i, exist_ok=True)
-            env["PROMETHEUS_MULTIPROC_DIR"] = prom_dir_i
-            logger.info(f"Set PROMETHEUS_MULTIPROC_DIR for DP {i}: {prom_dir_i}")
+            setup_dp_prometheus_dir(i, env["PROMETHEUS_MULTIPROC_DIR"], env)
 
         cmd = [
             sys.executable,
diff --git a/fastdeploy/metrics/prometheus_multiprocess_setup.py b/fastdeploy/metrics/prometheus_multiprocess_setup.py
index 509fb7d158c..42b7723bf3e 100644
--- a/fastdeploy/metrics/prometheus_multiprocess_setup.py
+++ b/fastdeploy/metrics/prometheus_multiprocess_setup.py
@@ -20,27 +20,56 @@
 
 from fastdeploy.utils import llm_logger
 
+_original_prom_dir = None
+
+
+def get_original_prom_dir():
+    """Return the PROMETHEUS_MULTIPROC_DIR before any dp suffix was appended."""
+    return _original_prom_dir
+
 
 def setup_multiprocess_prometheus():
-    """
-    Cleans and recreates the Prometheus multiprocess directory.
-    """
+    """Cleans and recreates the Prometheus multiprocess directory."""
+    global _original_prom_dir
 
     if "PROMETHEUS_MULTIPROC_DIR" not in os.environ:
-        base_dir = "/tmp/prom_main"
-        instance_id = str(uuid.uuid4())
-        prom_dir = f"{base_dir}_{instance_id}"
+        prom_dir = f"/tmp/prom_main_{uuid.uuid4()}"
         if os.path.exists(prom_dir):
             shutil.rmtree(prom_dir, ignore_errors=True)
         os.makedirs(prom_dir, exist_ok=True)
-        llm_logger.info(f"PROMETHEUS_MULTIPROC_DIR is set to be {prom_dir}")
         os.environ["PROMETHEUS_MULTIPROC_DIR"] = prom_dir
+        _original_prom_dir = prom_dir
+        llm_logger.info(f"PROMETHEUS_MULTIPROC_DIR is set to be {prom_dir}")
         return prom_dir
-    else:
-        prom_dir = os.environ["PROMETHEUS_MULTIPROC_DIR"]
-        llm_logger.warning(
-            f"Found PROMETHEUS_MULTIPROC_DIR:{prom_dir} was set by user. "
-            "you will find inaccurate metrics. Unset the variable "
-            "will properly handle cleanup."
-        )
-        return os.environ["PROMETHEUS_MULTIPROC_DIR"]
+
+    user_dir = os.environ["PROMETHEUS_MULTIPROC_DIR"]
+    _original_prom_dir = user_dir
+    os.makedirs(user_dir, exist_ok=True)
+    llm_logger.info(f"PROMETHEUS_MULTIPROC_DIR is set to {user_dir}")
+    return user_dir
+
+
+def setup_dp_prometheus_dir(dp_id, base_dir, env_dict=None):
+    """Set up an isolated PROMETHEUS_MULTIPROC_DIR subdirectory for a DP rank.
+
+    For DP0: moves existing .db files from base_dir into dp0/ and updates env.
+    mmap writes remain valid after rename on the same filesystem.
+    For DP1+: creates dp{i}/ subdirectory and updates env. Fork triggers PID
+    change → prometheus_client reset → new .db files in the subdirectory.
+
+    Args:
+        dp_id: Data parallel rank id.
+        base_dir: Original PROMETHEUS_MULTIPROC_DIR (before any dp suffix).
+        env_dict: If provided, write to this dict instead of os.environ.
+    """
+    prom_dir_dp = os.path.join(base_dir, f"dp{dp_id}")
+    os.makedirs(prom_dir_dp, exist_ok=True)
+    if dp_id == 0 and os.path.isdir(base_dir):
+        for fname in os.listdir(base_dir):
+            src = os.path.join(base_dir, fname)
+            if os.path.isfile(src) and fname.endswith(".db"):
+                os.rename(src, os.path.join(prom_dir_dp, fname))
+                llm_logger.info(f"Moved {src} -> {prom_dir_dp}")
+    target = env_dict if env_dict is not None else os.environ
+    target["PROMETHEUS_MULTIPROC_DIR"] = prom_dir_dp
+    llm_logger.info(f"Set PROMETHEUS_MULTIPROC_DIR for DP {dp_id}: {prom_dir_dp}")
diff --git a/tests/entrypoints/openai/test_multi_api_server.py b/tests/entrypoints/openai/test_multi_api_server.py
index a333ee6de0c..c039dcfbc65 100644
--- a/tests/entrypoints/openai/test_multi_api_server.py
+++ b/tests/entrypoints/openai/test_multi_api_server.py
@@ -231,7 +231,7 @@ def capture_popen(*args, **kwargs):
         for i, prom_dir in enumerate(prom_dirs):
             # The directory should contain the server index (0 or 1)
             # to uniquely identify each server's metrics directory
-            self.assertIn(f"_dp{i}", prom_dir, f"PROMETHEUS_MULTIPROC_DIR for server {i} should contain _dp{i}")
+            self.assertIn(f"/dp{i}", prom_dir, f"PROMETHEUS_MULTIPROC_DIR for server {i} should contain /dp{i}")
 
 
 if __name__ == "__main__":
diff --git a/tests/metrics/test_prometheus_multiprocess_setup.py b/tests/metrics/test_prometheus_multiprocess_setup.py
index 5ccc960d522..36508503150 100644
--- a/tests/metrics/test_prometheus_multiprocess_setup.py
+++ b/tests/metrics/test_prometheus_multiprocess_setup.py
@@ -51,15 +51,11 @@ def test_when_env_var_already_set(self):
         test_dir = "/tmp/existing_dir"
         os.environ["PROMETHEUS_MULTIPROC_DIR"] = test_dir
 
-        with patch("fastdeploy.utils.llm_logger.warning") as mock_logger:
+        with patch("fastdeploy.utils.llm_logger.info") as mock_logger:
             result = setup_multiprocess_prometheus()
 
             assert result == test_dir
-            mock_logger.assert_called_once_with(
-                "Found PROMETHEUS_MULTIPROC_DIR:/tmp/existing_dir was set by user. "
-                "you will find inaccurate metrics. Unset the variable "
-                "will properly handle cleanup."
-            )
+            mock_logger.assert_called_once_with(f"PROMETHEUS_MULTIPROC_DIR is set to {test_dir}")
 
     def test_cleanup_failure_handling(self):
         """测试清理目录失败时的处理"""