SAR image usually becomes very difficult when precise orbit data of SAR platform is not available. A SAR rectification method based on image simulation is proposed in this paper. The simulated SAR image is generated by means of Digital Elevation Model （DEM） and the known orbit data

then image matching is performed between the simulated and the real SAR image to identify some pairs of corresponding points. The position differences of these corresponding points are caused by the imprecision of the orbit data

and can be used to correct the rectification residuals. In this paper

the common SAR image simulation algorithms are introduced briefly

and then the algorithm used to match real to the simulated image is presented

as well as the SAR rectification method based on simulated image. At last

an experiment on the proposed rectification method is made

in which a RADATSAR SGF image is rectified precisely by means of simulated SAR image. Moreover

except the image matching stage

all the procedures of this rectification can be done automatically

which is significant to the large-volume SAR image processing.