Abstract: The relations of thrust and specific impulse to inlet air flow and temperature are derived from theoretical analysis of solid fuel ramjet (SFRJ) performance.Then numerical simulation of the SFRJ performance is completed with these relations and the results show that the thrust increases with the inlet air flow and specific impulse also increases,but the rate of increasing slows down as the flow increases.When inlet air temperature rises,the thrust increases but the specific impulse decreases.However,the influence of the inlet air flow is greater than that of the air temperature and reasons for both of the influences are also discussed qualitatively.