diff --git a/example/bthread_tag_echo_c++/server.cpp b/example/bthread_tag_echo_c++/server.cpp
index 4086c4a003..ed453fc9d5 100644
--- a/example/bthread_tag_echo_c++/server.cpp
+++ b/example/bthread_tag_echo_c++/server.cpp
@@ -29,6 +29,8 @@ DEFINE_int32(port2, 8003, "TCP Port of this server");
 DEFINE_int32(tag1, 0, "Server1 tag");
 DEFINE_int32(tag2, 1, "Server2 tag");
 DEFINE_int32(tag3, 2, "Background task tag");
+DEFINE_int32(num_threads1, 4, "Number of threads of server1");
+DEFINE_int32(num_threads2, 4, "Number of threads of server2");
 DEFINE_int32(idle_timeout_s, -1,
              "Connection will be closed if there is no "
              "read/write operations during the last `idle_timeout_s'");
@@ -102,6 +104,7 @@ int main(int argc, char* argv[]) {
     options1.max_concurrency = FLAGS_max_concurrency;
     options1.internal_port = FLAGS_internal_port1;
     options1.bthread_tag = FLAGS_tag1;
+    options1.num_threads = FLAGS_num_threads1;
     if (server1.Start(FLAGS_port1, &options1) != 0) {
         LOG(ERROR) << "Fail to start EchoServer";
         return -1;
@@ -127,6 +130,7 @@ int main(int argc, char* argv[]) {
     options2.max_concurrency = FLAGS_max_concurrency;
     options2.internal_port = FLAGS_internal_port2;
     options2.bthread_tag = FLAGS_tag2;
+    options2.num_threads = FLAGS_num_threads2;
     if (server2.Start(FLAGS_port2, &options2) != 0) {
         LOG(ERROR) << "Fail to start EchoServer";
         return -1;
diff --git a/src/brpc/server.cpp b/src/brpc/server.cpp
index 9d938c6bc9..0b3316cbe6 100644
--- a/src/brpc/server.cpp
+++ b/src/brpc/server.cpp
@@ -149,7 +149,7 @@ ServerOptions::ServerOptions()
     , health_reporter(NULL)
     , rtmp_service(NULL)
     , redis_service(NULL)
-    , bthread_tag(BTHREAD_TAG_DEFAULT) {
+    , bthread_tag(BTHREAD_TAG_INVALID) {
     if (s_ncore > 0) {
         num_threads = s_ncore + 1;
     }
@@ -902,6 +902,17 @@ int Server::StartInternal(const butil::EndPoint& endpoint,
         _tl_options = ThreadLocalOptions();
     }
 
+    auto original_bthread_tag = _options.bthread_tag;
+    if (original_bthread_tag == BTHREAD_TAG_INVALID) {
+        _options.bthread_tag = BTHREAD_TAG_DEFAULT;
+    }
+    if (_options.bthread_tag < BTHREAD_TAG_DEFAULT ||
+        _options.bthread_tag >= FLAGS_task_group_ntags) {
+        LOG(ERROR) << "Fail to set tag " << _options.bthread_tag << ", tag range is ["
+                   << BTHREAD_TAG_DEFAULT << ":" << FLAGS_task_group_ntags << ")";
+        return -1;
+    }
+
     if (_options.bthread_init_count != 0 &&
         _options.bthread_init_fn != NULL) {
         // Create some special bthreads to call the init functions. The
@@ -1020,7 +1031,16 @@ int Server::StartInternal(const butil::EndPoint& endpoint,
         if (_options.num_threads < BTHREAD_MIN_CONCURRENCY) {
             _options.num_threads = BTHREAD_MIN_CONCURRENCY;
         }
-        bthread_setconcurrency(_options.num_threads);
+        int res;
+        if (original_bthread_tag == BTHREAD_TAG_INVALID) {
+            res = bthread_setconcurrency(_options.num_threads);
+        } else {
+            res = bthread_setconcurrency_by_tag(_options.num_threads, _options.bthread_tag);
+        }
+        if (res != 0) {
+            LOG(ERROR) << "Invalid set bthread concurrency to " << _options.num_threads;
+            return -1;
+        }
     }
 
     for (MethodMap::iterator it = _method_map.begin();
@@ -1085,12 +1105,6 @@ int Server::StartInternal(const butil::EndPoint& endpoint,
                 return -1;
             }
             _am->_use_rdma = _options.use_rdma;
-            if (_options.bthread_tag < BTHREAD_TAG_DEFAULT ||
-                _options.bthread_tag >= FLAGS_task_group_ntags) {
-                LOG(ERROR) << "Fail to set tag " << _options.bthread_tag << ", tag range is ["
-                           << BTHREAD_TAG_DEFAULT << ":" << FLAGS_task_group_ntags << ")";
-                return -1;
-            }
             _am->_bthread_tag = _options.bthread_tag;
         }
         // Set `_status' to RUNNING before accepting connections
diff --git a/src/bthread/bthread.cpp b/src/bthread/bthread.cpp
index bd8c3efdea..8b02ff892b 100644
--- a/src/bthread/bthread.cpp
+++ b/src/bthread/bthread.cpp
@@ -389,18 +389,14 @@ int bthread_setconcurrency_by_tag(int num, bthread_tag_t tag) {
         bthread::never_set_bthread_concurrency_by_tag = false;
         return 0;
     }
+    auto c = bthread::get_or_new_task_control();
     BAIDU_SCOPED_LOCK(bthread::g_task_control_mutex);
-    auto c = bthread::get_task_control();
-    if (c == NULL) {
-        bthread::FLAGS_bthread_concurrency_by_tag = 0;
-        return 0;
-    }
     auto ngroup = c->concurrency();
     auto tag_ngroup = c->concurrency(tag);
     auto add = num - tag_ngroup;
     if (ngroup + add > bthread::FLAGS_bthread_concurrency) {
         LOG(ERROR) << "Fail to set concurrency by tag " << tag
-                   << ", Whole concurrency larger than bthread_concurrency";
+                   << ", Total concurrency larger than bthread_concurrency";
         return EPERM;
     }
     auto added = 0;