Abstract: In machine vision systems,lens is mainly responsible for imaging object on photosensitive surface of image sensor.Based on machine vision systems, the mechanical compensated zoom was adopted, the Zemax software was used to design a visible multifocal zoom lens system that could be applied in machine vision systems to address some specific situation while different magnification were required but working distance remained unchanged during production. The system has the working distance from 290 mm to 340 mm and the focal length changing from 10 mm to 100 mm, which makes 10 times multifocal zoom possible. The results shows that for this multifocal zoom lens,the maximum distortion is less than 1%, and it can best hold 1/3 inch CCD image sensor.The system imaging performance was assessed by modulation transfer function(MTF)，and MTF is greater than 0.3 at the frequency of 100 lp/mm, which meets the imaging demands.