Abstract: At present, most of the mining area construction is based on backfilling the hilly and gully area to level the site. For this special artificial geological structure, it is easy to be eroded and destroyed by water hazards, and the possible sources of water hazards are often multiple and difficult to determine.Taking the foundation water hazard of a mining area in Shanxi as an example, through detailed field investigation and hydrological drilling, the capillary water zone and stable water level of the fill foundation in the study area were determined, and the water source was preliminarily determined. On this basis, 28 water samples were taken, including 14 target water samples in the subsidence area and 14 water samples from possible water sources.The water samples were fully analyzed and tested for water quality. By means of mathematical statistics,Piper diagram, correlation analysis,water quality type comparison analysis method, hierarchical clustering method, ion ratio coefficient, the chemical characteristics, water quality type and chemical origin of groundwater under filling ground in mining area were comprehensively analyzed, and the specific sources of water hazards were determined.The results show that the target water sample and the possible source water cations in the subsidence area are dominated by K++Na+, and the anions in the target water samples in the sedimentation area are all dominated by HCO-3,and the water quality type is HCO3·Cl-Na·Mg , HCO3-Na and HCO3·SO4·Cl-Na. It is possible that HCO-3 is the main anion in the source water samples except for sandstone fissure water, and Cl- is the dominant anion in the rest of the samples.. According to the comprehensive comparison, the groundwater characteristics of the subsidence area and the sandstone fissure water are the most closely, its main source is sandstone fissure water recharge, followed by coal mine sewage and rainwater infiltration. The research results can provide a theoretical method for judging the water hazards of this type of landfill foundation, and play an early warning role for the subsequent pretreatment of similar landfill foundations.