Linear motion device is widely used in various industries. In this paper, a linear motion device design method is proposed for the test system with large load mass, large impact velocity and short acceleration time.According to this paper, the design of linear motion device is explicated, the structure of linear motion device is described, and the working principle is stated. Also, the three-dimensional model design of the components in linear moving device is carried out based on UG, and the sub-structure is illuminated. The finite element simulation analysis of each part in the catapult device is carried out based on Nastran. Conclusively, the structural deformation and stress of each part of the linear motion device are obtained, verifying the feasibility of linear motion device structure design.