In the past, most scholars have analyzed the characteristics of aerodynamic noise by studying the steady flow field of the rearview mirror. This paper aims to reveal the fundamental cause of the aerodynamic noise by studying the transient flow characteristics of the rearview mirror wake field, and reduce the aerodynamic noise by means of transient flow control. In this paper, the wind tunnel PIV test is used to capture the transient flow in the wake field of the rearview mirror, after the average treatment the steady flow field image obtained is consistent with the result of simulation, which verifies the accuracy of the flow field simulation method. Then, the LES turbulence model is used to simulate the flow field, and the transient flow characteristics of the rearview mirror are studied. The results show that, in the wake of the rearview mirror, there are some vortexes similar to the flow around the cylinder called Karman Vortex Street. In both horizontal and vertical directions, these vortexes are respectively separated from the upper and lower edges of the rearview mirror. Accompanied by a significantly periodic shedding, they continue to extend back until dissipated. The turbulence pulsation caused by this process is the root cause of the aerodynamic noise of the rearview mirror. The accuracy of the simulation method of aerodynamic noise is verified by the wind tunnel noise test. Using the simulation to propose the optimization scheme of the modeling, so as to reduces the pulsation of turbulence in the wake of the rearview mirror, this paper reduces the aerodynamic noise of the rearview mirror by controlling the transient flow.