A hypersonic vehicle, where the injection surface was reasonably partitioned, was analyzed in order to enhance the cost-effectiveness of wall mass injection for high-speed vehicles. Numerical simulations were conducted to get sample data in order to construct surrogate models. A multi-objective optimization of the injection flow rates of different surface partitions was conducted based on surrogate models by using non-dominated sorting genetic algorithm II (NSGA-II), targeting the reduction of total heat flux and drag. The uniform mass injection scheme reduced total drag by 14.05%, friction drag by 38%, total heat flux by 35.92%, and peak heat flux by 1.38% compared with the no mass injection case under the conditions of 50 km altitude, Mach 15 freestream, 5° angle of attack, and a total air injection flow rate of 50 g/s. The optimized mass injection case reduced total drag by 22.56%, friction drag by 53.96%, total heat flux by 53.40%, and peak heat flux by 30.77%. Results indicate that the optimized mass injection case injects more cooling medium on regions with high aerodynamic and thermal loads, such as the nose and leading edges of the wings compared with the uniform mass injection case. This optimized case leverages the attachment and cumulative effects of the injected mass flow along the high-speed main flow, improves the distribution of surface film thickness and significantly enhances both the drag and heat reduction effects and efficiency of the overall and the critical local location, while maintaining a constant total injection flow rate.