Objective To design a constant-force extrusion unit to meet the functional requirements of the prosthesis socket. Methods Based on the operational principle that the constant-force derives from offsetting of the positive and negative stiffness, the leaf spring was simulated based on the finite element analysis software. According to the simulation result of the leaf spring, the coefficient of spring stiffness was calculated. The constant-force unit after processing and assembling was tested by compression experiment. Results The simulation result was consistent with experimental result and the constant force of extrusion unit obtained an error about 2% within 3.5-mm range. Conclusions The constant-force characteristic is confirmed by experiment, which lays the foundation of realizing the time-shared and load-bearing hand prosthesis socket.