Abstract: The range history of bistatic synthetic aperture radar(SAR) echo is more complicated than the monostatic case,which increases the difficulty of educing the three imaging factors in chirp scaling algorithm.At present,most of the bistatic SAR processing method processes the bistatic SAR echo according to the bistatic characteristic, but this paper processes the bistatic SAR echo as monostatic SAR echo through transfering the bistatic range course into monostatic range course and introducing the bistatic speed ratio.Further more, it analyzes the error of the method of processing bistatic SAR echo as monostatic case under the situation of transational invariant mode and transational variant mode,which provides the guideness for choosing parameters during SAR imaging process.