Abstract: As a cooling device for the traction converter in the car, the noise of cooling tower aggravates the noise pollution seriously. In this paper, taking a cooling tower as the research object, the numerical simulation of flow field and sound field is carried out. In the steady-state simulation of flow field, the velocity distribution in cooling tower and the pressure distribution on the blade are analyzed. In the transient simulation of flow field, the vortex distribution at the blade and the pressure pulsation around the blade are analyzed, and location of the noise source and the cause of the noise are analyzed qualitatively. In the simulation of sound field, the transient results of flow field are transformed into the frequency domain as the sound source of cooling tower, and the sound source, spatial distribution and spectrum characteristics are analyzed.