diff --git a/douzero/dmc/utils.py b/douzero/dmc/utils.py
index 1b350b2..4002be0 100644
--- a/douzero/dmc/utils.py
+++ b/douzero/dmc/utils.py
@@ -123,11 +123,13 @@ def act(i, device, batch_queues, model, flags):
                 type_buf[mul_obs["position"]].append(2)
                 size[mul_obs["position"]] += 1
             while True:
-
-                with torch.no_grad():
-                    agent_output = model.forward(position, obs['z_batch'], obs['x_batch'], flags=flags)
-                _action_idx = int(agent_output['action'].cpu().detach().numpy())
-                action = obs['legal_actions'][_action_idx]
+                if len(obs['legal_actions']) > 1:
+                    with torch.no_grad():
+                        agent_output = model.forward(position, obs['z_batch'], obs['x_batch'], flags=flags)
+                    _action_idx = int(agent_output['action'].cpu().detach().numpy())
+                    action = obs['legal_actions'][_action_idx]
+                else:
+                    action = obs['legal_actions'][0]
                 if flags.old_model and position != 'bidding':
                     obs_action_buf[position].append(_cards2tensor(action))
                     obs_x_no_action[position].append(env_output['obs_x_no_action'])