Objective To observe the CT imaging findings of patients with sacroiliac joint lesions of ankylosing spondylitis (AS) and analyze their relationship with pathological features. Methods The clinical data of 76 patients with sacroiliac joint lesions of AS were retrospectively analyzed. All patients were given X-ray and CT examination. The grades diagnosis of AS sacroiliac joint lesions was compared between X-ray and CT. The CT imaging findings of patients with AS sacroiliac joint lesions were observed, and their relationship with pathological features was analyzed. Results The number of cases of grades II and III AS sacroiliac joint lesions by CT was higher than that by X-ray (P<0.05). CT examination showed that the AS sacroiliac joint lesions mainly affected bilateral side, iliac articular surface and synovial membrane. Common changes of AS sacroiliac joint lesions were articular cartilage calcification, joint space changes, sub-articular osteosclerosis and sacroiliac ligament calcification, and the changes could be clearly reflected by CT findings. Conclusion CT for AS sacroiliac joint lesions helps to improve the detection rate. CT findings can accurately reflect the different pathological features of AS sacroiliac joint lesions and provide assistance for diagnosis and treatment of this disease.