Abstract: In 2024, according to the exploration idea of "fracture-cavity gas reservoirs formed after fracture reconstruction of carbonate rock", three exploration wells were deployed in the Ordovician subsalt area of Ordos Basin to test gas and obtain high-yield industrial gas flow, revealing good exploration potential for the subsalt fracture-cavity gas reservoirs. However, the high-yield and enrichment regularity and comprehensive prediction model of fracture-cavity gas reservoirs are still unclear, making it difficult to determine favorable zones and achieve drilling targets. Therefore, based on cores, thin sections, seismic data, logging data, and production performances, this paper investigates the basic geological conditions and high-yield and enrichment mechanism of the Ordovician subsalt fracture-cavity gas reservoir in Ordos Basin. The results show as follows. (1)The subsalt fracture-cavity gas reservoirs have dual source hydrocarbon supply conditions of the Upper Paleozoic coal measures and Lower Paleozoic marine source rocks, of which the latter are the main source rocks, with the maximum hydrocarbon generation intensity of 1.2×10⁸m³/km² and sufficient hydrocarbon supply capacity. (2)The reservoir spaces of the subsalt fracture-cavity units are mainly composed of fractures and dissolution pores developed along the fracture zone, mixed with a small amount of matrix intergranular pores. The average porosity can reach more than 10 %, and the average permeability can reach up to 10 mD, demonstrating good reservoir performance. (3)The subsalt faults and associated fracture systems can not only improve the physical properties of dolomite reservoirs and form fracture-cavities with good reservoir performance, but also communicate source rocks with reservoirs, thus providing effective channels for oil and gas to accumulate in fracture-cavity reservoirs. (4)The thick layer of gypsum-salt rock developed in the 6th submember of Member 5 of Majiagou Formation serves as the regional cap rock for the fracture-cavity gas reservoir. The gypsum-salt rock developed in the 10th submember of Member 5 of Majiagou Formation, as well as the Member 3 of Majiagou Formation, serves as the cap rock overlying on the gas reservoir. Moreover, the tight carbonate rocks around the fracture-cavities form lateral sealing, and those good preservation conditions are conducive to natural gas enrichment and formation of fracture-cavity gas reservoirs. Through comprehensive evaluation, it has been preliminarily determined that the favorable exploration area for the Ordovician subsalt fracture-cavity gas reservoirs is about 2.5×10⁴km², and the estimated natural gas reserves can reach 5000×10⁸m³, indicating great exploration potential. It is an important direction and real target for exploration of the Ordovician subsalt natural gas.