The patent discloses a lens barrel driving system and a backlash correction method thereof. In such system, a zoom photo-interrupter (PI) is used to detect the movement of a zooming barrel and generate a first count value. The movement of a focusing barrel corresponds to the movement of the zooming barrel, so that when the zooming barrel is driven to move from an initial position to a first zooming position or from the first zoom position to a second zoom position, the focusing barrel moves correspondingly and its movement triggers a home PI to generate a second count value. Upon the generation of the second count value, a predetermined value is used to replace the first count value so as to correct the error caused by backlash of lens barrels.