The optical properties of the electro-wetting liquid zoom lens and the theory of zoom lens design were analyzed. Make the focal length of each element be variable and list the equations of the liquid lens zoom system. An initial liquid zoom lens structure by utilizing PSO and balance aberrations was studied by using optical design software. A 6×(20~120mm) zoom ratio liquid lens zoom system with four pieces of liquid lens was designed. The MTF at 66 lp/mm of this system at each focal length are greater than 0.3, and distortion is less than 2%, which meets the design requirements.