Abstract: The soluble egg antigen of Schistosoma japonicum was fractionated into 20 individual isoelectric point (pI) fractions with different pIs ranging from 1.86-11.40 by isoelectric focusing (IEF). The fractions were tested for humoral and cellular responses, as well as in vitro granuloma formations.The results indicated that the fractions in the acidic region(pI 3.78-5.54)may play an important role in granuloma elicitation in schistosomiasis japonica,and antibodies are also involved in the regulation of granuloma formation especially at the early stage (5 week postinfection).