Abstract: Wumishan Formation in Jixian System is the main-developed thermal storage formation in Tianjin, and the research on this layer mainly focuses on the temperature field, dynamic field, water chemistry field and surface water reinjection of the thermal reservoir, with little research on the karst fracture of thermal storage. In this paper, the authors analyzed and compared the completion and logging data of over 100 geothermal wells in Wumishan Formation in Tianjin to summarize the development of karst fractures of Class I and II in different structural units of Wumishan Formation, the burial depth of the thermal storage roof, the water inflow per unit of geothermal wells, the overlying different strata, and the development law of karst fractures. The results show that the karst fractures of Wumishan Formation are relatively developed, and the distance between the leakage site and the buried depth of the thermal storage roof plate is concentrated at a shallow distance of 100 m. The karst at the top of the hot reservoir is relatively developed, and fracture development is not greatly affected by different strata overlying the layer. The correlation between the fracture development and the burial depth of the roof of the layer is not obvious, but the overall fracture development tends to decrease slightly with the increase of the burial depth of the roof plate. The unit water inflow of geothermal wells increases with the increase of fracture development, and the heat storage fracture ratio is concentrated between 0.1 and 0.4. Under the influence of structure, the fractures of heat storage structure are more developed in the tensile fault structural zone, fault intersection and anticline axis. The research results could provide some references for the effective development and utilization of geothermal energy and geothermal drilling in Wumishan Formation of Tianjin.