Rheumatoid factor is one of the specific indicators of rheumatoid arthritis, which is important for the diagnosis of rheumatoid arthritis. Rheumatoid factor is an autoantibody produced by the abnormal function of the immune system in the human body, which is unable to recognize the normal tissue components of the body and treats them as foreign “foreign bodies”, inducing abnormal immune reactions and releasing them in large quantities in the human serum. In the 1980s, rheumatoid factor was first detected in the serum of patients with rheumatoid arthritis by foreign medical doctors. Since then, several studies have confirmed that rheumatoid factor has a high positive rate in the serum of patients with rheumatoid arthritis, but a low positive rate in other types of arthritis, non-rheumatic diseases and healthy people, so rheumatoid factor is important for the diagnosis and differential diagnosis of rheumatoid arthritis. Therefore, rheumatoid factor is also included as one of the classification criteria for rheumatoid arthritis. However, it should be noted that elevated rheumatoid factor alone without the manifestation of joint swelling and pain is not diagnostic of rheumatoid arthritis. With the current research, it is found that a few healthy elderly people, patients with viral hepatitis B, cirrhosis, and tuberculosis infection can also have positive rheumatoid factor, but they are mostly mildly elevated. In addition, autoimmune diseases such as systemic lupus erythematosus and dry syndrome can also be seen as rheumatoid factor positive due to abnormal immune function of the body. Therefore, the most common cause of rheumatoid factor elevation is rheumatoid arthritis, but a definitive diagnosis needs to be made in conjunction with joint symptoms. Once a patient has an elevated rheumatoid factor, he or she should visit a rheumatologist as soon as possible for a comprehensive analysis to find the cause.