The common one-off locking devices and repeated locking devices at domestic and overseas for magnetic bearing flywheels are introduced and their structures and working principles are analyzed. The research status of locking protection devices for magnetic bearing flywheels and their applications in satellite attitude control systems are summarized. The foreign one-off inner and outer locking devices are introduced. Combining the scheme construction of locking devices, the application situations of different locking devices are presented. To remedy the defect of one-off locking device which can not repeat locking and releasing, the development of domestic repeated locking devices is reviewed. The repeated inner locking device based on self-locking of wedge and the repeated clamping locking device are emphatically analyzed. Finally, the developing prospect of locking protection technology is expected. It points out that the inner repeatable locking device based on single actuator, the repeatable locking device with high locking stiffness and damping, and the testing method to verify protection function will be primary research directions of locking protection technology for magnetic bearing flywheels.