Human leukocyte antigen B27 is known as the human leukocyte antigen, and most of the Chinese population is negative for this antigen, which is within the normal range, while a small percentage of the population, about 5%, will be positive for human leukocyte antigen B27. For people who are positive for human leukocyte antigen B27, they are prone to ankylosing spondylitis, which is diagnosed if the patient also has significant lumbosacral pain, and a sacroiliac joint MRI or CT exam is performed to see sacroiliac arthritis. Human leukocyte antigen B27, therefore, is of great clinical significance for the diagnosis of ankylosing spondylitis. Although ankylosing spondylitis cannot be cured at present, early diagnosis as well as control will result in ideal control of the disease.