diff --git a/documentation/doxygen/kernel.h b/documentation/doxygen/kernel.h
index 15f6983e078..288688bfe6e 100644
--- a/documentation/doxygen/kernel.h
+++ b/documentation/doxygen/kernel.h
@@ -32,10 +32,10 @@
  * round-robin scheduling is used for this case.
  * - The time of scheduler to choose the next highest ready thread is determinant.
  * - There are four status in thread management
- *	-# Initialization
- *	-# Running/Ready
- *	-# Blocked
- *	-# Closed
+ *  -# Initialization
+ *  -# Running/Ready
+ *  -# Blocked
+ *  -# Closed
  * - The number of threads in the system is unlimited, only related with RAM.
  */
 
@@ -95,6 +95,15 @@
  * - The send action for communication facilities is also safe for interrupt service routine.
  */
 
+/**
+ * @defgroup Signal Signal
+ * @brief signal is used for thread kill etc.
+ *
+ * A signal (also known as a soft interrupt signal), from a software perspective,
+ * is a simulation of interrupt mechanism. When it comes to its principle,
+ * thread receiving a signal is similar to processor receiving an interrupt request.
+ */
+
 /**
  * @defgroup MM Memory Management
  * @brief memory management for memory pool and heap memory
diff --git a/include/rtdef.h b/include/rtdef.h
index 2fc3bd671c6..6985bb8f51a 100644
--- a/include/rtdef.h
+++ b/include/rtdef.h
@@ -1024,6 +1024,11 @@ struct rt_ipc_object
     rt_list_t suspend_thread;                 /**< threads pended on this resource */
 };
 
+/**
+ * @addtogroup semaphore
+ * @{
+ */
+
 #ifdef RT_USING_SEMAPHORE
 /**
  * Semaphore structure
@@ -1039,6 +1044,13 @@ struct rt_semaphore
 typedef struct rt_semaphore *rt_sem_t;
 #endif /* RT_USING_SEMAPHORE */
 
+/**@}*/
+
+/**
+ * @addtogroup mutex
+ * @{
+ */
+
 #ifdef RT_USING_MUTEX
 /**
  * Mutual exclusion (mutex) structure
@@ -1059,6 +1071,13 @@ struct rt_mutex
 typedef struct rt_mutex *rt_mutex_t;
 #endif /* RT_USING_MUTEX */
 
+/**@}*/
+
+/**
+ * @addtogroup event
+ * @{
+ */
+
 #ifdef RT_USING_EVENT
 /**
  * flag definitions in event
@@ -1080,6 +1099,13 @@ struct rt_event
 typedef struct rt_event *rt_event_t;
 #endif /* RT_USING_EVENT */
 
+/**@}*/
+
+/**
+ * @addtogroup mailbox
+ * @{
+ */
+
 #ifdef RT_USING_MAILBOX
 /**
  * mailbox structure
@@ -1102,6 +1128,13 @@ struct rt_mailbox
 typedef struct rt_mailbox *rt_mailbox_t;
 #endif /* RT_USING_MAILBOX */
 
+/**@}*/
+
+/**
+ * @addtogroup messagequeue
+ * @{
+ */
+
 #ifdef RT_USING_MESSAGEQUEUE
 /**
  * message queue structure
@@ -1129,6 +1162,8 @@ typedef struct rt_messagequeue *rt_mq_t;
 
 /**@}*/
 
+/**@}*/
+
 /**
  * @addtogroup MM
  */
diff --git a/include/rtthread.h b/include/rtthread.h
index 87383d3428c..43caf895ac4 100644
--- a/include/rtthread.h
+++ b/include/rtthread.h
@@ -246,7 +246,7 @@ void rt_scheduler_ipi_handler(int vector, void *param);
 /**@}*/
 
 /**
- * @addtogroup Signals
+ * @addtogroup Signal
  * @{
  */
 #ifdef RT_USING_SIGNALS
@@ -403,6 +403,11 @@ rt_err_t rt_thread_suspend_to_list(rt_thread_t thread, rt_list_t *susp_list, int
 /* only for a suspended thread, and caller must hold the scheduler lock */
 rt_err_t rt_susp_list_enqueue(rt_list_t *susp_list, rt_thread_t thread, int ipc_flags);
 
+/**
+ * @addtogroup semaphore
+ * @{
+ */
+
 #ifdef RT_USING_SEMAPHORE
 /*
  * semaphore interface
@@ -425,6 +430,13 @@ rt_err_t rt_sem_release(rt_sem_t sem);
 rt_err_t rt_sem_control(rt_sem_t sem, int cmd, void *arg);
 #endif /* RT_USING_SEMAPHORE */
 
+/**@}*/
+
+/**
+ * @addtogroup mutex
+ * @{
+ */
+
 #ifdef RT_USING_MUTEX
 /*
  * mutex interface
@@ -457,6 +469,13 @@ rt_inline rt_ubase_t rt_mutex_get_hold(rt_mutex_t mutex)
 
 #endif /* RT_USING_MUTEX */
 
+/**@}*/
+
+/**
+ * @addtogroup event
+ * @{
+ */
+
 #ifdef RT_USING_EVENT
 /*
  * event interface
@@ -487,6 +506,13 @@ rt_err_t rt_event_recv_killable(rt_event_t   event,
 rt_err_t rt_event_control(rt_event_t event, int cmd, void *arg);
 #endif /* RT_USING_EVENT */
 
+/**@}*/
+
+/**
+ * @addtogroup mailbox
+ * @{
+ */
+
 #ifdef RT_USING_MAILBOX
 /*
  * mailbox interface
@@ -521,6 +547,12 @@ rt_err_t rt_mb_recv_killable(rt_mailbox_t mb, rt_ubase_t *value, rt_int32_t time
 rt_err_t rt_mb_control(rt_mailbox_t mb, int cmd, void *arg);
 #endif /* RT_USING_MAILBOX */
 
+/**@}*/
+
+/**
+ * @addtogroup messagequeue
+ * @{
+ */
 #ifdef RT_USING_MESSAGEQUEUE
 
 struct rt_mq_message
@@ -599,6 +631,8 @@ rt_ssize_t rt_mq_recv_prio(rt_mq_t mq,
 #endif /* RT_USING_MESSAGEQUEUE_PRIORITY */
 #endif /* RT_USING_MESSAGEQUEUE */
 
+/**@}*/
+
 /* defunct */
 void rt_thread_defunct_enqueue(rt_thread_t thread);
 rt_thread_t rt_thread_defunct_dequeue(void);