diff --git a/python/sglang/srt/server_args.py b/python/sglang/srt/server_args.py
index 92fbcb575..7ca69f470 100644
--- a/python/sglang/srt/server_args.py
+++ b/python/sglang/srt/server_args.py
@@ -3266,9 +3266,12 @@ class ServerArgs:
         if self.mem_fraction_static is None:
             # Constant meta data (e.g., from attention backend)
             reserved_mem = 512
+            effective_chunked_prefill_size = self.chunked_prefill_size // (
+                self.dp_size if self.enable_dp_attention and self.dp_size > 1 else 1
+            )
             # For activation during large prefill
             if self.chunked_prefill_size > 0:
-                reserved_mem += max(self.chunked_prefill_size, 2048) * 1.5
+                reserved_mem += max(effective_chunked_prefill_size, 2048) * 1.5
             else:
                 reserved_mem += max(self.max_prefill_tokens, 2048) * 1.5
             # For cuda graphs