Abstract：Mineral association, ore structures and textures of the Bairendaba Ag polymetallic ore deposit in Keshiketeng banner were confirmed. Wall rock alterations are silicification, potassic alteration, sericitization, phyllic alteration, chloritization, fluoritization, carbonation and argillation. The mineralization process can be divided into four stages: porodic pyrite-quartz stage, arsenopyrite-iron rich sphalerite-pyrrhotite-quartz stage, polymetallic sulphide-quartz stage and fluorite-carbonate-quartz. Polymetallic sulphide-quartz stage is the main stage of silver mineralization. Previous publications on the study of fluid inclusion indicated that the characteristics of fluid inclusion are gas-liquid phases, moderate or low temperature, low salinity, and CO2 bearing. Based on tectonic setting, geological characters and fluid inclusion characters of the deposit, the Bairendaba deposit might be an epithermal silver deposit or a silver orogenic deposit, or superposition of both.