diff --git a/backend/app/services/simulation_manager.py b/backend/app/services/simulation_manager.py
index bda876cd..ff63d020 100644
--- a/backend/app/services/simulation_manager.py
+++ b/backend/app/services/simulation_manager.py
@@ -496,12 +496,24 @@ class SimulationManager:
         if platform is None:
             platform = state.get_default_platform()
 
+        if platform not in {"twitter", "reddit"}:
+            raise ValueError(f"不支持的平台: {platform}")
+
         sim_dir = self._get_simulation_dir(simulation_id)
-        profile_path = os.path.join(sim_dir, f"{platform}_profiles.json")
+        profile_path = os.path.join(
+            sim_dir,
+            "twitter_profiles.csv" if platform == "twitter" else "reddit_profiles.json",
+        )
         
         if not os.path.exists(profile_path):
             return []
-        
+
+        if platform == "twitter":
+            import csv
+
+            with open(profile_path, 'r', encoding='utf-8', newline='') as f:
+                return list(csv.DictReader(f))
+
         with open(profile_path, 'r', encoding='utf-8') as f:
             return json.load(f)
     
diff --git a/backend/tests/test_platform_profiles.py b/backend/tests/test_platform_profiles.py
new file mode 100644
index 00000000..f3883bda
--- /dev/null
+++ b/backend/tests/test_platform_profiles.py
@@ -0,0 +1,55 @@
+import csv
+import json
+
+import pytest
+
+from app.services.simulation_manager import SimulationManager, SimulationState
+
+
+def _manager(tmp_path, *, twitter, reddit):
+    manager = SimulationManager()
+    manager.SIMULATION_DATA_DIR = str(tmp_path)
+    state = SimulationState(
+        simulation_id="sim_test",
+        project_id="proj_test",
+        graph_id="graph_test",
+        enable_twitter=twitter,
+        enable_reddit=reddit,
+    )
+    manager._save_simulation_state(state)
+    return manager, tmp_path / "sim_test"
+
+
+def test_twitter_default_reads_generated_csv(tmp_path):
+    manager, sim_dir = _manager(tmp_path, twitter=True, reddit=False)
+    with (sim_dir / "twitter_profiles.csv").open("w", encoding="utf-8", newline="") as handle:
+        writer = csv.DictWriter(handle, fieldnames=["agent_id", "name"])
+        writer.writeheader()
+        writer.writerow({"agent_id": "0", "name": "Alice"})
+
+    assert manager.get_profiles("sim_test") == [{"agent_id": "0", "name": "Alice"}]
+
+
+def test_reddit_default_preserves_json_behavior(tmp_path):
+    manager, sim_dir = _manager(tmp_path, twitter=False, reddit=True)
+    profiles = [{"user_id": 0, "username": "alice"}]
+    (sim_dir / "reddit_profiles.json").write_text(json.dumps(profiles), encoding="utf-8")
+
+    assert manager.get_profiles("sim_test") == profiles
+
+
+def test_explicit_platform_overrides_dual_platform_default(tmp_path):
+    manager, sim_dir = _manager(tmp_path, twitter=True, reddit=True)
+    with (sim_dir / "twitter_profiles.csv").open("w", encoding="utf-8", newline="") as handle:
+        writer = csv.DictWriter(handle, fieldnames=["agent_id", "name"])
+        writer.writeheader()
+        writer.writerow({"agent_id": "1", "name": "Bob"})
+
+    assert manager.get_profiles("sim_test", platform="twitter")[0]["name"] == "Bob"
+
+
+def test_invalid_platform_is_rejected(tmp_path):
+    manager, _ = _manager(tmp_path, twitter=True, reddit=True)
+
+    with pytest.raises(ValueError, match="不支持的平台"):
+        manager.get_profiles("sim_test", platform="../state")