Objective: To investigate the imaging features and differential diagnosis of sacral insufficiency fractures. Methods: The imaging findings of 45 patients with sacral insufficiency fractures confirmed by imaging examination and follow-up were analyzed retrospectively. Among the 45 patients, 42 underwent MRI, 45 underwent CT, 16 underwent X-ray, and 12 underwent ECT. Results: The positive rate of X-ray was 37.5% featured by linear radiolucency accompanying by osteosclerosis. The positive rate of CT was 55.6% featured by linear radiolucency combined with marginal sclerosis. Other cases showed sacrum inhomogeneous or mixed bony density. The positive rate of MRI was 100% with the character of massive patchy bone marrow edema in sacrum. Among them, 81% of cases showed typical fracture line, 26 cases showed low signal fracture line on both T1WI and T2WI. 8 cases showed low signal fracture line on T1WI and high signal on T2WI. Conclusion: The imaging diagnosis of sacral insufficiency fracture has certain characteristics, especially MRI , which can improve the accurate diagnosis rate obviously and to avoid the excessive examination and thearpy.