Abstract: Schistosoma japonicum eggs were homogenized in phosphate buffered saline (PBS). The precipitate was extracted with 8 M urea. The chemical and immunological properties of the urea soluble antigens (JEU) were compared with those of the aqueous soluble antigens (JSEA) .The total antigenic activity units of JEU were 2.83 times those of JSEA in kinetic dependent enzyme linked immunosorbent assay (K-ELISA). By Bio-Gel A 50 m chromatography, a fraction JEG3 was obtained from JEU. JEG3 was stable and of high antigenic activity. As a diagnostic antigen in detection of antibody in patient sera by K-ELISA, JEG3 was more sensitive than JSEA. Analysis of JSEA and JEG3 by sodium dodecylsulfate/polyacrylamide gel electrophoresis (SDS-PAGE), enzyme linked immuno-electro-transfer blot (ELIB) of SDS-PAGE, electrofocusing electrophoresis and high performance liquid chromatography (HPLC) showed that JSEA and JEG3 contained different antigenic components. The molecular weight of JSEA components was less than 200,000 daltons. The molecular weight of the main components of JEGS was greater than 400,000 daltons.This study is one of the ptojects of the US-PRC cooperation in Science and Technolgy of Medicine and Public Health. This joint work is carried out by The Institute of Parasitic Diseases, Chinese Academy of Medical Sciences and The Centers for Disease Control, USA