Effects of O,2, and dose rate on the radiolysis of rabbit hepatic metallothionein-I(MT-I) in phosphate buffer solution at pH 8.0 have been studied. Active species (OH and H,2,O,2,) formed under irradiation principally attack the Zn-S bonds in the β-domain of MT-I and as a result, give birth to disulfide bonds, and the formation of disulfide bonds mainly occurs intramolecularly. The radiolysis of N,2,- or N,2,O-saturated MT-I solutions resulted in sulfhydryl-group-decrease with G,_SH_,=4.2 and 7.2 respectively, whereas G values of dimer ,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42650701&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42650704&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42650703&type=, were only 0.32 and 0.67.A short chain-reaction exists in the decrease of sulfhydryl groups when O,2,-saturated MT-I was irradiated, but it contributed little to ,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42650705&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42650686&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42650706&type=,. However, the damaged MT-I can be repaired completely by reduced glutathione. The reaction between H,2,O,2, and MT-I also was investigated, and k,2a,=10 mol•dm,-3,•s,-1, for RS-(MT-I)+H,2,O,2,→RSOH+OH,-, was abtained. Furthermore, the radiolysis mechanism of MT-I was disscussed on the basis of above mentioned results and good material balances were achieved.