Ankylosing spondylitis is a systemic disease of unknown cause, primarily characterized by chronic inflammation of the axial joints. It mainly affects the sacroiliac joints and leads to bony ankylosis, predominantly occurring in males, especially young males. The disease has a significant familial genetic tendency. The main symptoms are pain or discomfort in the lower back and back, typically occurring at night, accompanied by difficulty turning over. Stiffness is evident in the morning or after sitting for a long time, but symptoms may alleviate after physical activity. In young and middle-aged males showing these symptoms, ankylosing spondylitis should be suspected first. The main diagnostic methods include blood tests for HLA-B27, and imaging such as CT or MRI of the sacroiliac joints to detect any sacroiliitis. Diagnosis primarily relies on the combination of symptoms, HLA-B27 results, and sacroiliac joint CT findings.