diff --git a/src/llmtuner/data/aligner.py b/src/llmtuner/data/aligner.py
index 8144141c..5140f9d8 100644
--- a/src/llmtuner/data/aligner.py
+++ b/src/llmtuner/data/aligner.py
@@ -53,28 +53,32 @@ def convert_sharegpt(examples: Dict[str, List[Any]], dataset_attr: "DatasetAttr"
         if len(messages) == 0:
             continue
 
+        n_sys = 0
         prompt = []
         response = []
         for turn_idx, message in enumerate(messages):
-            if turn_idx % 2 == 0:
-                accept_tags = [dataset_attr.user_tag, dataset_attr.observation_tag]
-            else:
-                accept_tags = [dataset_attr.assistant_tag, dataset_attr.function_tag]
+            accept_tags = [dataset_attr.user_tag, dataset_attr.observation_tag, dataset_attr.assistant_tag, dataset_attr.function_tag]
 
-            if message[dataset_attr.role_tag] not in accept_tags:
+            if message[dataset_attr.role_tag] == "system":
+                outputs["system"].append(message[dataset_attr.content_tag])
+                n_sys += 1
+            elif message[dataset_attr.role_tag] not in accept_tags:
+                print("sytem attr", dataset_attr.system)
+                print("accepted tags", accept_tags)
                 raise ValueError("Invalid role tag in {}.".format(messages))
-
-            prompt.append(
-                {"role": tag_mapping[message[dataset_attr.role_tag]], "content": message[dataset_attr.content_tag]}
-            )
+            else:
+                prompt.append(
+                    {"role": tag_mapping[message[dataset_attr.role_tag]], "content": message[dataset_attr.content_tag]}
+                )
 
         last_message = prompt.pop(-1)
         response.append(last_message)
         outputs["prompt"].append(prompt)
         outputs["response"].append(response)
-        outputs["system"].append(examples[dataset_attr.system][i] if dataset_attr.system else "")
+        if n_sys == 0:
+            outputs["system"].append(examples[dataset_attr.system][i] if dataset_attr.system else "")
         outputs["tools"].append(examples[dataset_attr.tools][i] if dataset_attr.tools else "")
-
+        assert n_sys <= 1
     return outputs