Abstract: A ring aerodynamic throat concept of solid rocket motor controlled by secondary injection was simulated numerically.The influence and rules of secondary flow injection positions,injection angle,secondary flow rate and injector geometry parameters on the performance of aerodynamic throat were studied.The flow field character of aerodynamic throat was attained by calculation,namely: the starting point of sonic line from the downstream of secondary injection outlet.And the scope of injection positions for the existence of aerodynamic throat character was also attained.The results show that,the performance of aerodynamic throat can be obviously increased by making secondary flow injector close to the throat,increasing secondary flow rate or decreasing secondary flow injection angle.