diff --git a/components/bt/esp_ble_mesh/mesh_core/include/mesh_access.h b/components/bt/esp_ble_mesh/mesh_core/include/mesh_access.h
index 10304ff31..141cc6903 100644
--- a/components/bt/esp_ble_mesh/mesh_core/include/mesh_access.h
+++ b/components/bt/esp_ble_mesh/mesh_core/include/mesh_access.h
@@ -191,9 +191,9 @@ struct bt_mesh_model_op {
 #define BLE_MESH_MODEL_NONE ((struct bt_mesh_model []){})
 
 /** Length of a short Mesh MIC. */
-#define BLE_MESH_MIC_SHORT 4
+#define BLE_MESH_MIC_SHORT  4
 /** Length of a long Mesh MIC. */
-#define BLE_MESH_MIC_LONG 8
+#define BLE_MESH_MIC_LONG   8
 
 /** @def BLE_MESH_MODEL_OP_LEN
  *
diff --git a/components/bt/esp_ble_mesh/mesh_core/transport.c b/components/bt/esp_ble_mesh/mesh_core/transport.c
index 3bd0f20d1..56112c040 100644
--- a/components/bt/esp_ble_mesh/mesh_core/transport.c
+++ b/components/bt/esp_ble_mesh/mesh_core/transport.c
@@ -167,10 +167,16 @@ u8_t bt_mesh_get_seg_retrans_num(void)
 
 s32_t bt_mesh_get_seg_retrans_timeout(u8_t ttl)
 {
+    /* This function will be used when a client model sending an
+     * acknowledged message. And if the dst of a message is not
+     * a unicast address, the function will not be invoked.
+     * So we can directly use the SEG_RETRANSMIT_TIMEOUT_UNICAST
+     * macro here.
+     */
     struct seg_tx tx = {
         .ttl = ttl,
     };
-    return SEG_RETRANSMIT_TIMEOUT(&tx);
+    return SEG_RETRANSMIT_TIMEOUT_UNICAST(&tx);
 }
 
 void bt_mesh_set_hb_sub_dst(u16_t addr)
diff --git a/components/bt/esp_ble_mesh/mesh_models/client/client_common.c b/components/bt/esp_ble_mesh/mesh_models/client/client_common.c
index fed5408b9..fe5653b7b 100644
--- a/components/bt/esp_ble_mesh/mesh_models/client/client_common.c
+++ b/components/bt/esp_ble_mesh/mesh_models/client/client_common.c
@@ -185,7 +185,8 @@ static s32_t bt_mesh_client_calc_timeout(struct bt_mesh_msg_ctx *ctx,
         need_seg = true;    /* Needs segmentation */
     }
 
-    mic_size = (need_seg && net_buf_simple_tailroom(msg) >= 8U) ? 8U : 4U;
+    mic_size = (need_seg && net_buf_simple_tailroom(msg) >= BLE_MESH_MIC_LONG) ?
+                BLE_MESH_MIC_LONG : BLE_MESH_MIC_SHORT;
 
     if (need_seg) {
         /* Based on the message length, calculate how many segments are needed.
@@ -201,17 +202,14 @@ static s32_t bt_mesh_client_calc_timeout(struct bt_mesh_msg_ctx *ctx,
          * messages, but if there are other messages between any two retrans-
          * missions of the same segmented messages, then the whole time will
          * be longer.
+         *
+         * Since the transport behavior has been changed, i.e. start retransmit
+         * timer after the last segment is sent, so we can simplify the timeout
+         * calculation here. And the retransmit timer will be started event if
+         * the attempts reaches ZERO when the dst is a unicast address.
          */
-        if (duration + HCI_TIME_FOR_START_ADV < seg_retrans_to) {
-            s32_t seg_duration = seg_count * (duration + HCI_TIME_FOR_START_ADV);
-            time = (seg_duration + seg_retrans_to) * (seg_retrans_num - 1) + seg_duration;
-        } else {
-            /* If the duration is bigger than the segment retransmit timeout
-             * value. In this situation, the segment retransmit timeout value
-             * may need to be optimized based on the "Network Transmit" value.
-             */
-            time = seg_count * (duration + HCI_TIME_FOR_START_ADV) * seg_retrans_num;
-        }
+        s32_t seg_duration = seg_count * (duration + HCI_TIME_FOR_START_ADV);
+        time = (seg_duration + seg_retrans_to) * seg_retrans_num;
 
         BT_INFO("Original timeout %dms, calculated timeout %dms", timeout, time);