Abstract: The baiyun gold deposit is a polygenetic and mixedhydrothermal deposit controlled by reverse-thrust faults in the Liaohe group of Fengcheng county of eastern Liaoning. The metallic mineral constitution of the ore is simple, and the pyrite is the most principal Au-bearing mineral,its proportion in the metal minerals is up to 92%. On the basis of mineralization features of the deposit, the authors systematically determined and analysed the special physical property, chemical composition, geochemical and S-isotopic characters of the pyrite collected respectively from the formal wallrocks, i.e. metamorphic rocks, mineralized direct wallrocks, i.e. K-silicified.altered rocks and various ore types, then studied the typomorphic charcterictics of the pyrite and made an inquiry into its genesis and exploration significance.