A multiobjective optimization mathematical model with the largest lift,the highest efficiency and the smallest cavitation allowance was established for a certain type of engine coolant pump.Taking the lift curve without hump and impeller parameters as constraints,the objective model was optimized and solved by using the multiobjective genetic algorithm,and the global optimal solution was obtained.By using Fluent simulation software,the internal flow fields of the coolant pump that before and after optimization were simulated.The results show that after optimization,the internal pressure distribution of the impeller is more uniform,the backflow phenomenon between the blades is significantly reduced,and the energy loss is reduced;under the rated condition,the lift of the optimized coolant pump increases 0.86 m,the efficiency increases 6.6% and the cavitation allowance reduces 0.09 m.The simulation results show that this research method is more effective for the optimization of the engine coolant pump,which provides reference for the structural optimization of the coolant pump.