Ankylosing spondylitis belongs to the category of spondyloarthropathies among rheumatic diseases, and this group of spondyloarthropathies has a characteristic that is also known as seronegative spondyloarthropathies. Patients with this type of disease are negative for rheumatoid factor, so the vast majority of patients with ankylosing spondylitis will not have a positive rheumatoid factor. If a patient with ankylosing spondylitis is found to have a positive rheumatoid factor at the time of the test, there are several considerations: first, is it an error in the test, this time you need to redraw the blood and perform a retest of the index to see whether the rheumatoid-like factor is positive or negative. If the rheumatoid factor is still positive, the following diseases should be considered in conjunction with the patient’s symptoms: 1) whether the patient with ankylosing spondylitis has a history of tuberculosis or hepatitis. 2) whether the patient with ankylosing spondylitis has other small peripheral joints, especially the small joints of the hands and feet If there is symmetrical swelling and pain, and if there is also a positive rheumatoid factor, it is important to consider whether the patient with ankylosing spondylitis has a combination of rheumatoid arthritis. Second, patients with ankylosing spondylitis are older, and some elderly patients may also have a positive rheumatoid factor, but this time the rheumatoid factor is often positive in lower titers. Therefore, if a patient with ankylosing spondylitis appears clinically positive for rheumatoid factor, further diagnosis should be made in conjunction with the patient’s symptoms.