This invention provides a motor control method which comprises the steps of operating a motor at a fanless operation mode when a ambient temperature is lower than a lower temperature, operating the motor at a silent operation mode when the ambient temperature is higher than the lower temperature and lower than a higher temperature, and operating the motor at a cooling operation mode when the ambient temperature is higher than the higher temperature. When the motor operates at the fanless operation mode, the rotation speed of the motor is zero rpm. When the motor operates at the silent operation mode, the motor operates at a constant rotation speed. When the ambient temperature is higher than the higher temperature, the rotation speed of the motor is a linear function of the temperature and varies between the higher temperature and a maximum temperature corresponding to the full rotation speed of the motor.