The Middle-Upper Yanchang Formation in the Tianhuan Depression, Ordos Basin, is rich in oil and gas resources and has great exploration potential. However, due to its location in the western margin of the basin, the tectonic activities are complicated and the fault distribution and reservoir control mechanism are unknown.Based on core, imaging logging, calcite C—O isotope and U-Pb isotope dating experiments on fracture surface, the development characteristics and formation stages of Chang-6~Chang-8 Member faults in Hongde area are studied, and the controlling effect of faults on hydrocarbon accumulation is discussed. The results show that: ① The fractures in Hongde area are mostly concentrated in the lower combination of the Yanchang Formation, mainly in vertical and high-angle shear fractures. The fractures are partially filled with calcite and quartz, and obvious traces of overoil can be seen. ② The fracture strikes in the NEE-SW direction are predominant, followed by the near EW direction, mainly formed in the middle Early Cretaceous, late Early Cretaceous and early Late Cretaceous. The corresponding oxygen isotope conversion temperatures are 115.39℃, 139.83℃ and 153.55℃, respectively. ③ The U-Pb isotopic age of fractureface calcite is 170.6±6.1 Ma, 143±12 Ma, 104±32 Ma, and the activity period of the NEE-trending main fault is the Middle—Late Jurassic to Early Cretaceous, corresponding to the second—third act of Yanshanian Movement, which is consistent with the accumulation period of Chang-8 oil reservoir. It is concluded that the Yanchang Formation fault in the Tianhuan Depression improves the physical property of low permeability reservoir, plays a role of communication between oil source and migration channel, and promotes the migration and accumulation of oil and gas in remote source sand body.