These days micro lenses are used in many optical devices such as micro camera, cell phone and endoscopic medical imaging. In this work a passive autofocus system for a liquid lens with Dielectric Elastomer Actuator (DEA) which can easily achieve the function of auto focus without any active component such as ultrasonic or infrared in comparison with the conventional active focus system is proposed. In order to implement the technique a liquid lens with DEA membrane and a system to measure the sharpness of the image is used. The proposed method helps to find the best position of the lens by controlling the voltage which is applied to the membrane.