For studying the aerodynamic characteristics of rocket in the process of the rocket separating from the plane internally carried air-launched launch vehicle, especially when the rocket is at high angle of attack, CFD is applied to the simulation of rocket aerodynamic characteristics. Based on the improvement of rocket shape, the rocket aerodynamic characteristics with Mach number and angle of attack can be obtained. The analysis of the aerodynamic characteristics of the improved rocket model shows that the rocket tail improved into a convergent nozzle is of great benefit to the attitude adjustment. These analyses provide a theoretical foundation for the further research on rocket attitude stabilization and track design.