Abstract: Bistatic ISAR systems can receive echoes from different observation angles simultaneously, thus a finer image with more abundant information of a certain target can be obtained by fusing the two images attained with bistatic radars. However, the dis-match of dimensions and shapes of the two target images caused by bistatic angle highly complicates the image fusion process. This paper, based on the bistatic ISAR turn table model, proposes an ISAR image fusion method based on sub-aperture parameter estimation. The algorithm first extracts the Doppler difference between two sub-apertures of an isolated prominent scattering point to estimate the Rotation Velocity (RV) and half bistatic angle, then maps the two data sets from different observation angles onto a global coordinate system to perform the image fusion process, resulting in an ISAR image of higher quality. Finally, simulation experiments are provided to demonstrate the effectiveness of the method proposed.