In order to reduce the weight of the 2-DOF ammunition auto-loading manipulator and ensure the lightweight manipulator can still meet the dynamic and static performance requirements, the topology optimization method is adopted. The dynamic model of the ammunition auto-loading manipulator is established in RecurDyn and the coordinated simulation system is established in Matlab/Simulink. The position control of the ammunition auto-loading manipulator is realized by PID method. Use OptiStruct software platform to establish the finite element model of left and right arms. Use varied density topology optimization technology to lose weight of left and right arms. The results show that the design is reasonable, and the weight of the left and right arms is 36.6% lower than that of the original model. The optimization model can satisfy the performance requirements of stiffness.