Abstract: Ground-Based Synthetic Aperture Radar (GB-SAR) can achieve sub-millimetric deformation measurement accuracy, and has huge potential in monitoring displacement of both natural terrain and man-made structures. The data acquisition geometry of GB-SAR is characterized by highly sub-optimal aperture length, wide-swath, and full-field scenarios, which is different from that of traditional SAR modes. Therefore, most of the now existed imaging algorithms are very ineffective under GB-SAR cases. Aiming at this issue, an algorithm based on sub-image combination technique is proposed. Problems introduced by GB-SAR geometry are well addressed. The final image is formatted in a pseudo-polar coordinate. At last, the performance of this algorithm is validated both with numerical simulations and real GB-SAR data.