The multistage screw electric cylinder is more complex than the single stage screw electric cylinder in structure, and the transmission mechanism is more, and its efficiency loss link is increased relatively. As the core transmission mechanism of multistage electric cylinder, the transmission efficiency of the multistage screw mechanism directly affects the overall efficiency of the electric cylinder. By analyzing the structure of the multistage screw, the efficiency of the multistage screw is modeled and analyzed, and the efficiency formula of the multistage screw is derived. The change rules between the transmission efficiency of the multistage screw and the nominal diameter and the guide range of the screw were analyzed. According to the special requirement of electric cylinder structure, the electric cylinder efficiency as the goal, through the weighted function of nonlinear constrained optimal value optimization calculation, the structure parameters of the best combination were determined, the optimal efficiency of load changes impact on the levels of structure parameters was analyzed. The study results can provide a theoretical reference for the design of multistage electric cylinder.