diff --git a/slime/backends/megatron_utils/model.py b/slime/backends/megatron_utils/model.py
index 320a8188c5..8886f82732 100644
--- a/slime/backends/megatron_utils/model.py
+++ b/slime/backends/megatron_utils/model.py
@@ -500,6 +500,16 @@ def should_disable_forward_pre_hook(args: Namespace) -> bool:
     return args.use_distributed_optimizer and args.overlap_param_gather
 
 
+def finalize_model_grads_with_empty_cache(*args, **kwargs):
+    # trigger empty cache when there are less than 10% free memory before the final reduce scatter.
+    # TODO: this is an ad-hoc method and we should figure out why the oom happens in the first place.
+    device = torch.cuda.current_device()
+    free, total = torch.cuda.mem_get_info(device)
+    if free / total < 0.1:
+        clear_memory()
+    return finalize_model_grads(*args, **kwargs)
+
+
 def train(
     rollout_id: int,
     model: Sequence[DDP],
@@ -550,7 +560,7 @@ def train(
         config.param_sync_func = [model_chunk.start_param_sync for model_chunk in model]
         if len(model) == 1:
             config.param_sync_func = config.param_sync_func[0]
-    config.finalize_model_grads_func = finalize_model_grads
+    config.finalize_model_grads_func = finalize_model_grads_with_empty_cache
 
     pre_hook_enabled = False