Abstract: GB-SAR (Ground-based synthetic aperture radar) has been widely utilized to monitor surface deformations, which has a major limitation that they can only measure the one-dimensional (1-D) deformation along radar-target line of sight. To measure the 3-D deformations, multiple GB-SAR could be utilized together to observe one monitoring scene from different aspects. However, images acquired by different radar could present obviously different features, which could not be registered with the conventional method of polynomial curve fitting. Therefore, the paper presented a new image registration method applied for joint measurements of multiple GB-SAR. The method mainly included two key aspects: transformation of 3-D coordinate systems and relevance of homonymous projection points. Some reference points were firstly utilized to transform multiple GB-SAR and terrain information into a same coordinate system. Then homonymous projection points were relevant based on the projection principle of GB-SAR imaging. Experimental datasets acquired with two radar systems were utilized to preliminary validate the feasibility of the proposed method.