A fast radar imaging method for a buried object is presented.At first,backscatter data is computed with propagation. inside-layer expansion combining forward and backward method with spectral acceleration(PILE+FB.SA).Then,a conventional synthetic aperture radar(SAR)imaging procedure called back projection method is used to generate 2-D images.The choice of window functions is studied.A random rough surface with Gauss spectrum is used to simulate the ground.A tapered incident wave is chosen to reduce truncation errors.This method is proper for rough surface with any parameters with buried complex object.It is useful in realistic object detecting.