To enhance the meshing performance of a non-orthogonally offset profile-shifted helical face gear drive to meet the requirements of aviation power transmission, a tooth-surface modification design method for the driving pinion was proposed. Eight geometric control parameters of the tooth direction and tooth profile modification curve of the driving pinion were selected as optimization variables, a multi-objective optimization model was established to reduce the amplitude of load transmission error fluctuations, lower the contact flash temperature of tooth surfaces and achieve uniform load distribution on tooth surfaces. The NSGA-Ⅱ multi-objective genetic algorithm was employed to solve the optimization problem. Case-study results indicate that the optimized tooth-surface modification significantly decreases the fluctuation amplitude of the loaded transmission error, markedly reduces the maximum tooth contact flash temperature at the tooth tip of the helical face gear, and yields a more uniform load distribution on the tooth surface, which provides a theoretical reference for the design of compact and high-performance aero-power transmission system.