Abstract: At present, the equipment in the field of photoelectric reconnaissance develops lighter and smaller constantly, while the volume and weight of traditional zoom optical system cannot satisfy the load requirements of micro photoelectric reconnaissance platform. Therefore, the small unmanned aerial vehicle (UAV) and other reconnaissance platforms can only equip withprime lens, which limits the improvement of resolution, detection distance and reconnaissance ability. The liquid lens technology can adjust the focal length by using a single lens, which largely reduces the volume of the optical system, and has fast zoom response and wide zoom range. The optical system composed of liquid lens can fast zoom in a fixed small volume, which has broad application prospects in both military and civil fields. The theoretical basis and research methods of the predecessors were investigated and summarized. Firstly, five basic principles of liquid lens were briefly described, and their characteristics were analyzed respectively. Then, the research status of liquid lens at home and abroad were introduced. And finally, the merits and demerits of liquid lens, as well as its future development and research directions were indicated.