By employing the Computer Fluid Dynamics(CFD) software to simulate the process of a car trailing a large truck,the aerodynamic drag coefficient and the aerodynamic lift coefficient of the car in the process of trailing were obtained.The result showed that the aerodynamic drag coefficient gradually slowed down with the decrease of the distance between the two autos,and why the aerodynamic drag coefficient arrived at the minimum when the distance was two times of the car length,while the aerodynamic drag coef...