Abstract: This paper addresses the research of ground moving target imaging and posi-tioning in Synthetic Aperture Radar (SAR) system. First it analyzes the difference between ground moving target imaging process and that for stationary ones. The method brought forward in this paper uses the direction of road and bridge of the gazing ground as prior known knowledge, and it can accurately estimate the coordinates and velocities of the moving targets while t = 0. It means that the method can get the position of the moving targets and image them with the same precision as stationary targets imaging in SAR system. There is no special postulation in the proposed algorithm contrast to the conventional method which always assumes that the targets located on the vertical side of SAR at the point of t = 0. Finally two different forms of matched filters are given out for moving targets imaging and the different results are analyzed. The smearing and position shifting effect when using sta-tionary target matched filter to process the moving target echo is also analyzed at the last part.