［Purposes ］ Portal cranes are the core equipment for material handling in ports，and the design of their boom and balance system has a direct impact on the operating performance and energy consumption of the whole machine.This paper aims to optimize the position of the hinge point，the length of the rod，and the mass of the counterweight of the boom and balance system，so as to reduce the vertical drop of the lifting weight and the variation of the unbalanced moment of the boom and balance system.［Methods］ With the objective function of minimizing the vertical drop of the lifting weight during the luffing process and minimizing the variation of the unbalanced moment of the system，the position of the hinge point，the length of the rod，and the mass of the counterweight were used as the optimization design variables.According to the boundary constraints and the performance constraints of the actual working conditions，the optimized mathematical model of the boom and the balance system was established.Moreover，genetic algorithm and MATLAB programming were used to optimize and solve the model，so as to obtain the optimum design parameters.Finally，the multi -body dynamics model of the boom and balance system was developed，and ADAMS software was applied to simulate and analyze the luffing process of the boom and balance system.［Findings］ Compared with that before optimization，the vertical drop of the lifting weight after optimization is reduced by 17.65%，and the variation of the unbalanced moment of the boom and balance system is reduced by 83.26%.The simulation data of the vertical drop of the lifting weight is highly consistent with the theoretical data，which proves that the optimized mathematical model is credible.On this basis，the change rule of the load at the connecting hinge point of each rod with the luffing of the boom is analyzed，which provides a theoretical basis for the detailed design of the subsequent boom and balance system. ［Conclusions ］ The optimized design significantly reduces the energy consumption of the crane luffing process and provides technical support for the subsequent structural design of port handling equipment.