diff --git a/vllm_ascend/core/scheduler.py b/vllm_ascend/core/scheduler.py
index 627d5ea899..253dd2a158 100644
--- a/vllm_ascend/core/scheduler.py
+++ b/vllm_ascend/core/scheduler.py
@@ -444,7 +444,7 @@ def _check_watermark_for_prefill(self,
                                    self.block_size)
         req_blocks = self.kv_cache_manager.coordinator.get_blocks(
             request.request_id)
-        num_new_blocks = (num_required_blocks - len(req_blocks) -
+        num_new_blocks = (num_required_blocks - len(req_blocks[0]) -
                           len(computed_blocks))
         num_evictable_computed_blocks = sum(1 for blk in computed_blocks
                                             if blk.ref_cnt == 0)