In order to solve the difficulty of obtaining the overall tactical performance indicators of the aircraft through one optimal process in the solid rocket motor (SRM) design, and comprehensively considering the solid propulsion and the external trajectory, the two traditional optimal processes which are the optimization of scheme and the optimization of parameters of the SRM were combined to one design optimization program here. From the point of the overall tactical performance of the aircraft, the process of the integrated simulation of internal and external trajectory was established to get the parameters of the relevant parameters of the SRM. And the design optimization program which matches both the internal and external trajectory well was set up. Based on the integrated simulation of internal and external trajectory, The design of the SRM was optimized to avoid the multiple iterations and coordination of the two traditional optimal processes, so the design cost and period decrease.