Aiming at the problems that the large thrust of erecting mechanism and the high demand on carrying capacity of cylinder,the virtual prototype model is established by using the ADAMS software,the method of setting the size of the contact force to detect motion interference is proposed. Using the method,that joints pivot is parameterized,the maximum erecting force is regard as the objective function,the layout of joints pivot is optimized,the maximum force of electric cylinders in the erecting process is reduced. Aiming at the characteristics that its force is complicated and the stress distributed unbalanced in erecting process,the flexibility analysis on the stress of the triangular arm at the initial stage and the intermediate stage are carried out. The lightweight of the triangular arm is carried out by using topology optimization,so as to reducing the structural weight and the cost is saved.