CFD (computation fluid dynamics) was applied to simulate the vehicle windshield defrosting process. To solve the problem of slow defrosting in area A, a new method was proposed. Four defroster grilles were installed at airflow vents, which can rotate around their center axis. Combined with dynamic mesh, the transient defrosting process was calculated. The results show that, when grilles are deflected to 42 degrees, the Nusselt number of area A improves by 13.7%, making the grilles rotate at 0.0733 rad/s, and the grilles are back to the original position at 280s. Compared with the original model, the time required to defrost area A decreases by 60s. The frost covering area A is removed preferentially, which ensures that the driver's field of vision is clear and quick.