he micro-displacement actuator is one of the most important components in the active optics system of the primary mirror segment,which must meet the requirements of large stroke,high positioning accuracy and high load at the same time.With the increasing aperture of the telescope,the actuator should have a larger stroke while maintaining high precision and high load,which is a challenge for the design of the actuator.In order to find a feasible structure scheme of micro-displacement actuator and provide a clear reference for the actuator researchers,in this paper,according to the requirements arising from the development of large optical telescope,the actuators that are being used in the telescope and the actuators that have been designed and tested,including soft actuators to be used in the 30 meter telescope and other pre research actuators,are described in terms of specific structures,and the components of the actuators are sorted,summarized,classified and compared.Finally,the development trend of the micro-displacement actuator is prospected based on the advantages and disadvantages of various actuators.