The detailed influences of the free mach number, jet mach number, attack angle on the drag coefficient reduction were studied by high precise simulation of N-S(Navier-Stockes) equations. The Numerical results show good agreement with the experiments. It is indicated that the opposing jet is effective in reducing the aerodynamic heating and drag coefficient. Conclusions were got that the opposing jet enlarges the factors of affections by influencing the strength and the positions of the barrel shock, the mach disk and the recirculation region. It is believed that the drag coefficient turns out to be very sensitive to the flow field-s structure which is highly depended on the free mach number, jet mach number and attack angle due to the opposing jet.