Abstract: Ankle injury is a common form of human injury, and ankle rehabilitation has received more and more attention and research. The hybrid mechanism is used in the rehabilitation exercise after ankle injury, which can effectively improve the rehabilitation effect of the rehabilitation mechanical device. A 4- degree of freedom (2-UPU-PU)&R hybrid rehabilitation mechanism is proposed based on the analysis of the structural characteristics and motion form of human ankle joint. By using the modified K-G formula to analyze the degree of freedom of the ankle rehabilitation mechanism, the inverse solution of the position of the mechanism is solved based on the closed-loop vector method, and the working space of the mechanism is solved by using the search method. the limited output control system of position and speed is designed to verify that the designed mechanism can meet the needs of rehabilitation, ensure the safety of use, and provide theoretical guidance for the subsequent control system design.