With the development of information technology，optical communication becomes the main way of data communication. Optical switches are the core components in optical communication systems. Micro-electro-mechanical system（MEMS）has been widely used in the optical field with the features of miniaturization and integration，etc. MEMS optical switches not only retain the advantages of low loss and low crosstalk of traditional mechanical optical switches，but also have the advantages of small size，light weight，and short switching time. This paper introduces the principle of MEMS optical switch，describes the research progress of MEMS optical switch，and analyzes the advantages of MEMS optical switch. MEMS optical switches have characteristics such as fast response speed，high integration，low insertion loss，and good scalability，which have obvious advantages over traditional optical switches and show great potential for application.