Ankylosing spondylitis is a connective tissue disease, the cause of which is not yet clear and is associated with genetics, cold and damp invasion, immune factors, and infections. The details are as follows: 1, genetic: common in men, the incidence of first-degree relatives is 24%, 120 times higher than the normal population; 2, autoimmune factors: more important; 3, infections: patients with ankylosing spondylitis are mostly accompanied by iritis, chronic enteritis, diarrhea; 4, other causes: such as trauma, long-term exposure to wind, cold and damp factors, are prone to ankylosing spondylitis.