Abstract: Based on the result of sulfur isotope analysis, as well as element ratio and microelement data of the M28 anomaly area in the Chajianling orefield, with also lithologic and mineral identification, it is concluded that the Lower Permian Fanjiatun Formation in the M28 anomaly area belongs to sediment genesis. During the sedimentation and diagenesis of the strata, organic carbon adsorbed amount of metal elements, causing the high primary content of Ag-polymetal in the Fanjiatun Formation. It provides the material basis for the Ag-polymetal mineralization of the anomaly area.