Abstract: The echo data of airborne bistatic SAR has range space variance or range-azimuth space variance, so it is necessary to perform block imaging in airborne bistatic SAR focusing. Based on the slant range of airborne bistatic SAR, the range walk and range cure formulas of arbitrary point target in the observing scene are derived with the track decoupling formulas. After performing the range cell migration (RCM) correction, imaging region blocking rules are derived with the residual range cell migration (RCM) and quadratic phase error (QPE). Then imaging region blocking results of airborne bistatic SAR in various configuration are tested with the numerical simulations, moreover, influences of geometry parameters and system parameters on imaging region are also analyzed, and they provide theoretical guidance to imaging region blocking in bistatic SAR wide scene imaging.