diff --git a/src/W800_SDK_v1.00.10/src/bt/blehost/porting/w800/include/syscfg/syscfg.h b/src/W800_SDK_v1.00.10/src/bt/blehost/porting/w800/include/syscfg/syscfg.h
index 1b21cee..464c225 100644
--- a/src/W800_SDK_v1.00.10/src/bt/blehost/porting/w800/include/syscfg/syscfg.h
+++ b/src/W800_SDK_v1.00.10/src/bt/blehost/porting/w800/include/syscfg/syscfg.h
@@ -425,7 +425,7 @@
 
 /*** @apache-mynewt-nimble/nimble/host */
 #ifndef MYNEWT_VAL_BLE_ATT_PREFERRED_MTU
-#define MYNEWT_VAL_BLE_ATT_PREFERRED_MTU (512)
+#define MYNEWT_VAL_BLE_ATT_PREFERRED_MTU (256) // 512
 #endif
 
 #ifndef MYNEWT_VAL_BLE_ATT_SVR_FIND_INFO