Abstract: Taking the elevator mechanism of a loading and unloading automatic equipment as the research object, using the Lagrange equation and Ritz series method, the dynamic model of the ball screw vertical lifting system is established in centralized parameter method and distribution parameter method. The dynamic responses of the system are calculated by applying modal superposition principle and the reduced order method for solving differential equations. A corresponding MATLAB calculation program is developed to carry out the numerical analysis. The modal analysis of the system is carried out. The influence of different parameters on the displacement response of the work table are studied. According to the simulation results, the relative weakness of the system is analyzed, and the parameters of screw nut are selected. After the selection design, the mechanism runs more smoothly. The results show that the proposed dynamic modeling method and research results have guiding significance for the vibration characteristics analysis and structural design of the ball screw vertical lifting system.