diff --git a/lightx2v_platform/ops/attn/hygon_dcu/flash_attn.py b/lightx2v_platform/ops/attn/hygon_dcu/flash_attn.py
index d1fff4fe2..c9a4d0cfe 100644
--- a/lightx2v_platform/ops/attn/hygon_dcu/flash_attn.py
+++ b/lightx2v_platform/ops/attn/hygon_dcu/flash_attn.py
@@ -25,6 +25,24 @@
     FLASH_ATTN_AVAILABLE = False
 
 
+def _get_sparse_attn_topk(default: float = 0.4) -> float:
+    raw_topk = os.getenv("SPARSE_ATTN_TOPK", str(default))
+    try:
+        topk_value = float(raw_topk)
+    except (TypeError, ValueError):
+        logger.warning("Invalid SPARSE_ATTN_TOPK={!r}; falling back to {:.3f}", raw_topk, default)
+        return default
+
+    if not 0.0 < topk_value <= 1.0:
+        logger.warning(
+            "SPARSE_ATTN_TOPK={!r} is outside (0.0, 1.0]; falling back to {:.3f}",
+            raw_topk,
+            default,
+        )
+        return default
+    return topk_value
+
+
 @PLATFORM_ATTN_WEIGHT_REGISTER("flash_attn_hygon_dcu")
 class FlashAttnHygonDcu(AttnWeightTemplate):
     """
@@ -114,7 +132,7 @@ def half(x):
             softmax_scale = 1.0 / math.sqrt(q.shape[-1])
         # Use Flash Attention 2.6.1 (ROCm version) with varlen interface
         if SAPRDE_LINEAR_ATTN and int(os.getenv("USE_SLA", 0)) and q.shape[1] == k.shape[1]:
-            topk_value = float(os.getenv("SPARSE_ATTN_TOPK", "0.5"))
+            topk_value = _get_sparse_attn_topk()
 
             q = q_flat.unsqueeze(0)
             k = k_flat.unsqueeze(0)
@@ -124,7 +142,7 @@ def half(x):
                 q,
                 k,
                 v,
-                topk=0.4,
+                topk=topk_value,
             )
         else:
             output = flash_attn_varlen_func(