Abstract: For vehicles at high Mach number and high altitude in near space, CFD may not be able to provide accurate aerodynamic coefficients of the vehicles, for example, the drag force and the lift to drag ratio. The cause is now acknowledged as the rarefaction effect of the air that has not been taken into consideration in conventional CFD. The current numerical methods for rarefied gas flow are hard to be used in practice due to their enormous computation costs. An accurate and efficient numerical method is necessary. A rarefaction parameter Zh, which characterizes the effect induced by large mean free path and high shear strengths, was proposed in reference1 published in Acta Aerodynamica Sinica in 2018 by Chen Jie and Zhao Lei. Moreover, the relationship between effective viscosity and Zh was also proposed for the consideration of local rarefaction effect. In the present paper, this effective viscosity model is embed in the CFD to simulate a hypersonic flow over a blunt plate at Mach number 15. The results show that the drag calculated by the new model decreases and the lift-drag ratio increases, compared with that obtained by the conventional CFD method. This belaviour is qualitatively consistent with the existing flight test result. In addition, the computational cost is not be appreciably increased.