Abstract: In view of the all-weather requirements of automotive anti-collision radar system, the scattering and attenuation of the radar at 24, 35, 66 and 77 GHz respectively in rainfall is analyzed, and then the propagation model of triangular frequency modulation continuous wave in the rain medium is set up. The time-domain signal of the triangular frequency modulation continuous wave is simulated by Matlab after being through the rain medium, at different propagation distance and rainfall rate which have the influences on the performance of the automotive anti-collision radar. The conclusion shows that the attenuation degree of the amplitude of echo signal increases with the increase of propagation distance and rainfall rate, and rainfall rate has a more distinct influence.