This paper presents the design of an actuator with high efficiency and auto-locking ability which features an additional holding force in the power-off condition. The operating principle of the auto-locking structure is based on the concept of flux switching. In the paper, an analytical method for computing the cogging torque of the two operating states (the moving and holding states) is developed. It is investigated that the actuator develops a holding force in the power-off condition which can be safely turned on using the auto-locking mechanism The torque characteristics for the auto-locking structure are also investigated using analytical and finite element analysis methods (using ANSYS 3D FEA software). A prototype is constructed and the experimental results are used to verify and validate the simulation results.