diff --git a/backend/app/services/cosyvoice_service.py b/backend/app/services/cosyvoice_service.py
index 321f6a1..3685493 100644
--- a/backend/app/services/cosyvoice_service.py
+++ b/backend/app/services/cosyvoice_service.py
@@ -13,6 +13,11 @@ def synthesize_cosyvoice(text, speed=1.0, pitch=0, volume=1.0, instruction=None)
         'Content-Type': 'application/json'
     }
     
+    # 前端 pitch: -12~12 → API rate: 0.5~2.0（以1.0为中心）
+    pitch_ratio = max(0.5, min(2.0, 1.0 + pitch / 24))
+    # 前端 volume: 0~10 → API volume: 0~100
+    volume_int = int(max(0, min(100, volume * 10)))
+
     payload = {
         'model': 'cosyvoice-v3.5-flash',
         'input': {
@@ -20,6 +25,11 @@ def synthesize_cosyvoice(text, speed=1.0, pitch=0, volume=1.0, instruction=None)
             'voice': 'cosyvoice-v3.5-flash-bailian-e859a6e87823419f9c6b3eefb1a97dc3',
             'format': 'mp3',
             'sample_rate': 32000
+        },
+        'parameters': {
+            'rate': max(0.5, min(2.0, speed)),
+            'pitch': pitch_ratio,
+            'volume': volume_int
         }
     }