Abstract: The major serological antigen (MSA) involved in crude soluble egg antigen of S. japonicum (SEAj) has been isolated from the crude one by affinity chromatography and characterized by electrophoresis in previous studies carried out in our laboratory. In this study, the serological activity of MSA was further compared with that of SEAj to evaluate their value in serodiagnosis. The results showed that the sensitivity of both MSA and SEAj for the detection of antibody in patients with schistosomiasis japonica was comparable (91.67%). There was 1.2% false positive rate in normal serum with SEAj, but no positive false reaction was detected with MSA. The amount of antigen consumed in SEAj-ELISA is 2.5 times that consumed in MSA-ELISA, suggesting that MSA has higher serological activity.