Abstract: Three kinds of horse anti-sera against the venom of Agkistrodon halys (Palls),I.e.the crode whole serum,the antivenin purified by ammonium sulphate precipitation and the antivenin digested with pepsin and purified by ammonium sulphate precipitation were compared by polyacrylamide gel electrophoresis.The results show that the third kind of antivenin is apparently different from the other two kinds and it shows only one obvious the antibody protein band on polyacrylamide gel electrophoretic pattern.The antibody protein corresponds to the IgG of normal horse serum.