The scattering of the radar signal by the rough surface of the target in the infrared,microwave and THz wave field is universal.The research shows that the rough degree of the object is an important factor in determining the cross section of laser radar in the infrared field,while in the microwave field the effect of the rough degree of the object is a stochastic process,or a perturbation.The return power of the radar scattering cross section is the convolution of the height dispersion density distribution function of the rough surface and the impulse response function of the flat surface.Usually the effects of the convolution correspond to a δ function that acts on the impulse response function of the flat surface.