Abstract: This paper presents a 3D SAR imaging and multi-look processing algorithm in the variation of the velocity for the forward-looking ground penetrating radar (FLGPR).By using nonstationary convolution filter,the spectrum of the refocused image can be reconstructed directly from the spectrum of backscattered signal from the target area and the 3D target image is reconstructed after the inverse Fourier transform.By estimating the incidence angle of target,the refraction correction and the multi-look processing are accomplished.The effectiveness of the approach is demonstrated with experimental data set.