Distance sensing system and method of mobile communication device

This invention relates to a distance sensing system of a mobile communication device including a sensor sensing the distance to an object surface and outputting a number after processing it, a comparator electrically connecting to said sensor, having a first reference value and a second reference value and comparing them with said number in terms of the used state of the device then to output a first caution signal in session according to a comparison result, output a second caution signal at the standby state, a sound player electrically connecting to said comparator to play a sound containing a volume and a volume controller connecting to said comparator, so that, the two caution signals can alter said volume.