Abstract: The water resources in the piedmont hilly area at the northern foot of the Bogda Peak in the Tianshan Mountains are an important source of water for local industry, agriculture and residents' domestic use. In view of the increasingly serious loss of water resources in this area, taking Tiechanggou River Basin phreatic water aquifer as the research object, the spatial distribution and water-rich characteristics of the phreatic aquifer along the Tiechanggou River Basin, the way and amount of phreatic resource loss were studied and analyzed by means of hydrogeological mapping, surface geophysical exploration, hydrogeological drilling, numerical simulation and other means. The results show that the Quaternary alluvial-proluvial layer in the coalbed formation intersection area of Tiechanggou River and Badaowan syncline is thick in the south (upstream) and thin in the north (downstream), and the floor elevation of the loose layer is gradually decreasing along the river direction, which is basically consistent with the characteristics of the gully flow in front of the mountain. The unit water inflow (q) of the aquifer in this area is 0.146 L/（s·m）, the permeability coefficient (K) is 0.233 m/d, and the water richness of the aquifer is medium. The submerged flow field takes the surface collapse pit as the center and presents a typical falling funnel shape, and there is a concentrated channel between the groundwater aquifer and the underground gob in the subsidence pit area. FEFLOW numerical simulation was used to calculate the phreatic water leakage at the collapse pit, which was 86m3/h. This was basically consistent with the measured value of downhole water inflow. Coal mining is the main cause of the loss of diving resources in the middle and lower reaches of the Tiechanggou River. The collapsed cracks formed after mining are the main channels of the loss of diving resources. The engineering treatment of the collapsed cracks is the main way to protect the diving resources.