Abstract: Coal is the main energy source in China. The North China type coalfields account for 60% of China's total coalfield resources, and most mining areas have entered the deep mining stage, facing many problems such as unclear distribution patterns of water abundance in roof aquifers. Based on the geological and hydrogeological conditions of the mining area, this study selected the typical North China type coal field - Tianchen Well Tianqi No. 1 mining area 3 coal overlying aquifer as the research object. The thickness of the water-bearing medium was multiplied by a conversion coefficient, and factors such as sandstone content and sand mud combination layers were considered to construct the "Lithology Influencing Index" (LII), which quantitatively evaluates the water richness of the aquifer, Provide geological support for the prevention and control of coal mine water hazards.