In order to meet the requirements of high smoothness, high contact ratio and lightweight of gear transmission in the aerospace field. A macro parameters optimization design method for high contact ratio (HCR) spur gears is proposed. The influence laws of macro parameters of gears on tooth root bending strength, tooth contact strength, scuffing load capacity, and load sharing ratio between gear teeth were analyzed. Then, a multi-objective optimization mathematical model was established to obtain the optimal design parameters of HCR spur gear using maximum contact strength, maximum scuffing load capacity, and minimal mass as the objective function. The results show that there is a significant increase in gear contact strength and bending strength, and the time-varying meshing stiffness fluctuations and the load sharing ratio between gear teeth has decreased markedly.