diff --git a/examples/aflow/optimize.py b/examples/aflow/optimize.py
index 62df68585..d07eab993 100644
--- a/examples/aflow/optimize.py
+++ b/examples/aflow/optimize.py
@@ -72,7 +72,12 @@ def parse_args():
     parser.add_argument("--max_rounds", type=int, default=20, help="Max iteration rounds")
     parser.add_argument("--check_convergence", type=bool, default=True, help="Whether to enable early stop")
     parser.add_argument("--validation_rounds", type=int, default=5, help="Validation rounds")
-    parser.add_argument("--if_first_optimize", type=bool, default=True, help="Whether it's the first optimization")
+    parser.add_argument(
+        "--if_first_optimize",
+        type=lambda x: x.lower() == "true",
+        default=True,
+        help="Whether to download dataset for the first time",
+    )
     return parser.parse_args()
 
 
diff --git a/metagpt/ext/aflow/scripts/optimizer_utils/data_utils.py b/metagpt/ext/aflow/scripts/optimizer_utils/data_utils.py
index 2df161ed8..2a09e0820 100644
--- a/metagpt/ext/aflow/scripts/optimizer_utils/data_utils.py
+++ b/metagpt/ext/aflow/scripts/optimizer_utils/data_utils.py
@@ -18,7 +18,11 @@ class DataUtils:
     def load_results(self, path: str) -> list:
         result_path = os.path.join(path, "results.json")
         if os.path.exists(result_path):
-            return read_json_file(result_path, encoding="utf-8")
+            with open(result_path, "r") as json_file:
+                try:
+                    return json.load(json_file)
+                except json.JSONDecodeError:
+                    return []
         return []
 
     def get_top_rounds(self, sample: int, path=None, mode="Graph"):