Abstract: Anti-dsDNA antibodies of 69 cases(50 SLE and 19 other connective tissue diseased were measured with Crithidia luciliae immunofluorescence assay (CL-IF) and indirect hemag-glutination assay (IHA). ANA of there patients was also detected by indirect immunofluorescence at the same time. Active SLE group showed a higher percentage of positive test with CL-IF (95%) than with IHA (45%), the difference was significant (P<0.01). The author emphasized the importance of CL-IF in the evaluation of SLE activity, and its value in the differential diagnosis of active SLE.