Abstract: Based on the related parameters of formation water, combined with the spatial distribution of hydrocarbon reservoirs, this paper discussed the relationship between the chemical characteristics of formation water and the hydrocarbon accumulation and preservation in Hongshanzui?Chepaizi fault belt and its surrounding areas. In profile，the formation water types in Neogene Shawan formation and Lower Jurassic Badaowan formation are dominated by CaCl2, while in Lower Cretaceous Qingshuihe formation, Upper Jurassic Qigu formation andLower Jurassic Sangonghe formation they are dominated by NaHCO3. The total dissolved solid(TDS) or salinity of formation water in Shawan formation is the highest, the TDS in Qingshuihe formation is lower, and the TDS in Sangonghe formation is the lowest. For the Sodium?Chlorine coefficient, carbonate equilibrium coefficient and de?sulfuric acid coefficient, Sangonghe formation is the highest, and Qigu formation and Qingshuihe formation are lower. For the Calcium?Magnesium coefficient and Metamorphic coefficient, Shawan formation is the highest, Qingshuihe formation and Badaowan formation are lower. The comprehensive analyses show that the sealing property of Badaowan formation is the best, and those of Shawan formation and Qingshuihe formation are better, and those of Qigu formation and Sangonghe formation are poor. On the Plane, the sealing property of middle part of the study area in Qingshuihe formation is the best, while those of the north part of it in Qigu formation and the south part of it in Badaowan formation are the best. The sealing property of formation indicated by the chemical characteristics of formation water is consistent with the spatial distribution characteristics of hydrocarbon reservoirs, having important guiding significance on the hydrocarbon exploration in these areas