Abstract: Spherical motors are defined by the spherical structures. They have developed rapidly and got more and more research interest in recent years due to the capacity of multi-degree-of-freedom (DOF) motion in 3-D space and the feasibility in artificial intelligence, reaction sphere and etc. Spherical motors expand the rotor motion range, representing an important development direction of the motor industry in the future. Compared with the traditional single-DOF motor, the spherical motor has more complex structure and special motion mode, so the analysis and research of the spherical motor is different from that of the traditional single-DOF motor. In this paper, an overview of spherical motors is presented, with an emphasis on concept, development, mechanisms, topologies, design and optimization methods, and properties. The rotor position detection methods, control methods, rotor support methods and applications of spherical motors are also summarized. The key techniques and prospects of spherical motors are discussed and summarized.