Abstract: It is of great practical significance for the prevention and control of groudwater hazards in North China type coalfield to judge transmissivity-impermeability of faults by using karst hydrochemical characteristics of two fault walls. Taking karst groundwater of Taiyuan Formation on both sides of fault F₁₀₄ in Gubei coal mine as the research object, and based on the analysis of the hydrogeological conditions of two fault walls, main components sources and water-rock interaction differences were analyzed by using Piper trilinear diagram, ion combination ratio and principal component methods. Reverse hydrochemical simulation of karst groundwater was conducted by using PHREEQC software. Research results show that dissolution and precipitation of calcite and dolomite exist in the north and south areas; cation exchange and desulfurization in the south region are stronger than that in the north area; while oxidation of pyrite and dissolution of salt rock in the north area is more obvious than those in the south area; there are significant differences in the hydrochemical environment and water-rock interaction between the two areas. It is inferred that fault F₁₀₄ has a preferably water-resistance, and affects the oxidation-reduction environment and temperature differences of the two areas, which controlling the direction of groundwater runoff and the degree of water-rock interaction.