Abstract: The optimization design of balance spring cylinder of MD1200-YJ palletizing robot with low energy consumption is researched. Firstly, based on the conventional rigid body dynamics model of robot, an inverse dynamics model of shoulder joint considering the spring balance torque and load dynamic weight torque is established, and the energy consumption model is established combined with the motion parameters. Secondly, the 3-4-5 polynomial interpolation function is used to complete the trajectory planning of operational space terminal "door" type. Thirdly, taking the structural parameters and installation position parameters of the balance spring cylinder as design variables and their value range as constraint conditions, and taking the minimum maximum absolute value and the minimum fluctuation of shoulder joint torque as optimization objectives, NSGA-Ⅱ algorithm is used for multi-objective optimization solution. Finally, by comparison, the optimized shoulder joint torque and energy consumption are significantly reduced, and the dynamic performance is significantly improved, verifying the effectiveness of the optimization method.