The　bonding　interaction　and　hydrolytic　cleavage　of　oxidized　insulin　B　chain　with　ZnCl2　in　molar　ratios　of　1:1　1:2　and　1:3　at　pH　value　of　2.5　and　40　degrees　C　were　investigated　by　electrospray　ionization　mass　spectrometry　and　tandem　mass　spectrometry.　The　results　show　that　the　binding　sites　of　Zn2+　with　oxidized　insulin　B　chain　are　Arg22　and　imidazole　groups　of　His5,　His10,　which　leads　to　the　selective　cleavages　of　the　peptide　bonds　at　Asn3-Gln4,　His5-Leu6,　Gly8-Ser9　and　Glu21-Arg22　of　oxidized　insulin　B　chain.