Abstract:The carbonate rock karst thermal reservoir in the Xiong’an New Area is a highquality geothermal resource with significant development potential. Clarifying characteristics of the formation, evolution and development of karst fractures in the Wumishan Formation reservoir plays an important role in studying the formation and accumulation of geothermal resources, and is a prerequisite for the rational and effective exploitation of geothermal resources. Based on previous studies, the formation process of the Wumishan Formation, and geometric features of the karst fractures have been analyzed in detail based on data from outcrops, core sampling, rock slices, drilling, and well logging. The results show that the formation of karst and fractures in the Xiong’an New Area is closely related to tectonic activities, especially during the period from the late Indosinian movement to the Himalayan movement. During this period, the most favorable karst was formed. The average thickness and average interval of fracture zones are 4. 70 m and 4. 05 m, respectively, and the average proportion of reservoir thickness is 41. 90%. The trend of internal fractures in the reservoir is mainly northeast and the dip angle is mainly between 50° and 90°. The fracture frequency per area is 5. 34 pieces/m2. The average length and opening of fractures are 1. 20 m and 95. 16 μm, respectively. There are many types of filling materials in fractures, with dolomites, pyrites and quartzs being the most common. The formation contains lots of semifilled and unfilled fractures. Present ground stress helps to open fractures, and the fracture network is developed in the reservoir with good connectivity, which has a very good waterconducting and waterstoring performance and provides good conditions for the enrichment of geothermal resources in the reservoir.