Optical zoom system is a key element in many optical devices such as cameras and video cameras. It is a long-term goal to realize miniaturization of optical zoom system and increase the zoom ratio of the system. In this paper, a three-liquid self-zoom lens is developed, which has the self-zoom function under the action of applied voltage. Therefore, the lens element itself can be used as a simple optical zoom system. The self-zoom function of the system is verified by the Gaussian optical theory and Zemax simulation. The results show that the focal length range of the system is 378-424 mm, and the zoom ratio is 1.217, which achieves the expected target and has a certain reference value for the research of optical zoom systems.