Abstract: The circulating antigen （CAg） of schistosomiasis japonica from the sera of Schi-stosoma japonicum-infected rabbits was purified by immune-affinity chromatography. The purified CAg exhibited seven protein bands by SDS-PAGE. The molecular weights of them are 144,118, 100，88，63，57 and 46 kD respectively. These CAgs showed five sugar protein bands by PAS colouring. The molecular weights of these sugar proteins are 144,118，100, 63 and 57 kD respectively. The CAgs released from the ova of the schistosome contain 114 and 118 kD sugar proteins as shown by ELIB.