As a powerful geochronometer, the Re Os isotope system has been successfully used for precisely dating depositional age of limestone, however，the removal mechanisms of Re and Os from seawater are not yet fully understood. The major and trace elements, Re Os isotopes and TOC of the limestone from the Permian Triassic boundary interval of the global stratotype section and point (GSSP) at Meishan, Changxing, Zhejiang Province, have been used to contrain redox conditions of sedimentary environment. The study on the occurrence of Re and Os in the limestone demonstrates that Re occurs in the organic matter of limestone only under highly reducing conditions. Hence, Limestone can be targeted for Re Os dating only under reducing conditions. In contrast, Os removal from seawater to limestone can be found under various redox conditions. Authigenic minerals under oxic environments can enrich some Os, Thus,a high 187 Re/ 188 Os ratio can occur only in reducing sediments. The Os isotope system of authigenic materials that occurs in an oxic matine environment can be used as a paleo marine environmental tracer.