diff --git a/bsp/bluetrum/ab32vg1-ab-prougen/board/board.c b/bsp/bluetrum/ab32vg1-ab-prougen/board/board.c
index 32714f6a4de71cf2b27da94fabfc29197e618c42..4246a92d0bd3111bd8f43e35e7a8183cff387cf0 100644
--- a/bsp/bluetrum/ab32vg1-ab-prougen/board/board.c
+++ b/bsp/bluetrum/ab32vg1-ab-prougen/board/board.c
@@ -145,11 +145,6 @@ void rt_hw_board_init(void)
 #endif
 }
 
-void rt_hw_us_delay(rt_uint32_t us)
-{
-
-}
-
 RT_SECTION(".irq.cache")
 void cache_init(void)
 {
diff --git a/bsp/mini2440/drivers/board.c b/bsp/mini2440/drivers/board.c
index 4cc2dad409ce34db54d00f02071fdabbf815131d..05aa26a4c9547937909ba1d481773fdd024b94fb 100644
--- a/bsp/mini2440/drivers/board.c
+++ b/bsp/mini2440/drivers/board.c
@@ -122,9 +122,4 @@ void rt_hw_board_init(void)
 
 }
 
-void rt_hw_us_delay(rt_uint32_t us)
-{
-
-}
-
 /*@}*/
diff --git a/bsp/qemu-vexpress-a9/drivers/board.c b/bsp/qemu-vexpress-a9/drivers/board.c
index 84af3c1ccd82db7f38cd9a51dc2eb3399b51cded..2ee8e95bd58266470240ee23e7b253fa36811b13 100644
--- a/bsp/qemu-vexpress-a9/drivers/board.c
+++ b/bsp/qemu-vexpress-a9/drivers/board.c
@@ -56,7 +56,3 @@ void rt_hw_board_init(void)
 #endif
 }
 
-void rt_hw_us_delay(rt_uint32_t us)
-{
-
-}