Abstract: A device with function of automatically shutting down when dropped acquires an acceleration value detected by an acceleration sensor, and determines whether the acceleration value is more than a preset acceleration value. A timing unit is controlled to count time when the acceleration value is more than the preset acceleration value, and a travel distance of the device is calculated according to the acceleration value and the time period of the falling. If the travel distance of the device is more than a preset distance, a power management system is controlled to shut down a power supply to the device. A method for such function and system is also provided.