Whether anti-cyclic citrullinated peptide antibody 90Ru/ml is serious or not cannot be generalized. Anti-cyclic citrullinated peptide antibody is only a specific autoantibody for diagnosing rheumatoid arthritis, the value cannot reflect the severity of the disease, but should be based on the patient’s clinical symptoms and comprehensive judgment. The normal value of anti-cyclic citrullinated peptide antibody varies from hospital to hospital and from testing organization to testing organization, and most of them are less than 5 Ru/ml. If the anti-cyclic citrullinated peptide antibody of 90 Ru/ml is more than the normal range, and there is joint swelling and pain in the clinical manifestations, then the diagnostic criterion can be considered as the diagnosis of rheumatoid arthritis, and active anti-rheumatism treatment is needed. If only the value is higher than the normal range without any clinical symptoms, it does not indicate rheumatoid arthritis, and regular follow-up is needed. The titer of anti-cyclic citrullinated peptide antibody and the degree of increase in the value is a factor in determining the prognosis of rheumatoid arthritis, and a higher value may be a factor in the poor prognosis. Therefore, the severity of the disease cannot be determined solely on the basis of the anti-cyclic citrullinated peptide antibody values. If there is any abnormality in the test, it is recommended to go to the rheumatology and immunology department of the hospital for comprehensive evaluation and treatment.