In clinical practice, HLA-B27 is a human leukocyte antigen, a type of leukocyte with high specificity. In clinical practice, it is an important indicator for the diagnosis of ankylosing spondylitis, gouty arthritis, rheumatoid arthritis and rheumatoid arthritis. In ankylosing spondylitis, the B27 test is positive and the positive rate is up to 90% or more, so the B27 test is an indispensable one for the diagnosis of ankylosing spondylitis. A definitive diagnosis can be made basically based on clinical symptoms combined with a radiograph or CT film of the spine. In addition, b27 is associated with many other diseases and is very meaningful for the diagnosis of these diseases.