diff --git a/libraries/HAL_Drivers/drv_pwm.c b/libraries/HAL_Drivers/drv_pwm.c
index 6543ced..a0e7b63 100644
--- a/libraries/HAL_Drivers/drv_pwm.c
+++ b/libraries/HAL_Drivers/drv_pwm.c
@@ -264,14 +264,6 @@ static rt_err_t drv_pwm_get(TIM_HandleTypeDef *htim, struct rt_pwm_configuration
     rt_uint64_t tim_clock;
 
     tim_clock = tim_clock_get(htim);
-    if (__HAL_TIM_GET_CLOCKDIVISION(htim) == TIM_CLOCKDIVISION_DIV2)
-    {
-        tim_clock = tim_clock / 2;
-    }
-    else if (__HAL_TIM_GET_CLOCKDIVISION(htim) == TIM_CLOCKDIVISION_DIV4)
-    {
-        tim_clock = tim_clock / 4;
-    }
 
     /* Convert nanosecond to frequency and duty cycle. 1s = 1 * 1000 * 1000 * 1000 ns */
     tim_clock /= 1000000UL;
@@ -357,6 +349,7 @@ static rt_err_t drv_pwm_set_pulse(TIM_HandleTypeDef *htim, struct rt_pwm_configu
     tim_clock /= 1000000UL;
 
     period = (__HAL_TIM_GET_AUTORELOAD(htim) + 1) * (htim->Instance->PSC + 1) * 1000UL / tim_clock;
+    configuration->pulse = period - configuration->pulse; // 改为低电平有效，故需要计算一下低电平的脉宽
     pulse = (rt_uint64_t)configuration->pulse * (__HAL_TIM_GET_AUTORELOAD(htim) + 1) / period;
 
     if (pulse < MIN_PULSE)
@@ -452,7 +445,7 @@ static rt_err_t stm32_hw_pwm_init(struct stm32_pwm *device)
 
     oc_config.OCMode = TIM_OCMODE_PWM1;
     oc_config.Pulse = 0;
-    oc_config.OCPolarity = TIM_OCPOLARITY_HIGH;
+    oc_config.OCPolarity = TIM_OCPOLARITY_LOW;
     oc_config.OCFastMode = TIM_OCFAST_DISABLE;
     oc_config.OCNIdleState = TIM_OCNIDLESTATE_RESET;
     oc_config.OCIdleState  = TIM_OCIDLESTATE_RESET;