Human leukocyte antigen B27, or HLA-B27, is a specific antigen on leukocytes, a marker antibody for rheumatoid arthritis, and is also closely associated with ankylosing spondylitis. HLA-B27 is immunologically classified and is usually detected by chemofluorescence and sequence-specific techniques after venous blood collection.HLA-B27, as a marker antibody for rheumatoid arthritis, has a high specificity, and is useful in the diagnosis of rheumatoid arthritis in which the symptoms are not obvious in the early stages. In addition, the positive rate of HLA-B27 in the normal population is only 4%~7%, while in ankylosing spondylitis patients, the positive rate of HLA-B27 can reach 90%, so it is said that there is a close relationship between HLA-B27 and ankylosing spondylitis. Specific diagnosis and treatment should be carried out under the guidance of physicians.