At present, there are many clinical reports on the treatment of sacroiliac joint (SIJ) dysfunction by manipulation of oblique-pulling (MOP). However, the specific mechanism of MOP on the SIJ remains unclear. This study aimed to investigate the effect of MOP on the biomechanics of SIJ and the effect of the anterior sacroiliac ligament (ASL) on the stability of sacroiliac joint. Firstly, nine cadaveric pelvises were applied by MOP-F1 and MOP-F2. Then, segmental ASL resection and SIJ fixation were performed. The range of motion of SIJ were observed in all procedures. Under MOP-F1 and F2, the average total angles were 0.84° and 1.52°, and the displacements were 0.61 mm and 0.98 mm, respectively. Compared with MOP-F1, MOP-F2 caused greater obviously rotation angles and displacements of SIJ. In addition, SIJ mobility significantly increased after complete resection of ASL. The increase was mainly due to the transection of the upper part of ASL. Conclusively, MOP-F2 caused greater rotation angles and displacements of SIJ and it was a more effective manipulation. The ASL played an important role in maintaining the stability of the SIJ, and the upper part of ASL contributed more to the stability.