Abstract: Objective To establish the method to examine the anti-Sa antibody and study its value in diagnosing rheumatoid arthritis (RA). Method The optimal conditions to examine the anti-Sa antibody by Western blot have been selected through three groups of complete cross tests. We examined the anti-Sa antibody in the sera of patients with RA or other autoimmunity diseases and healthy people. The RF was examined by immuno latex agglutination. Results The sensitivity of anti-Sa antibody to RA is 42.7%and its specificity is 100%, the sensitivity of RF is 72.0%and its specificity is 79.2%. Conclusion The specificity of the anti-Sa antibody is higher than that of RF, so the diagnostic value of anti-Sa antibody was better than that of RF.