In recent years, remarkable exploration results have been achieved in the Ordovician marine carbonate reservoirs in the Fuxian area, located in southeast Ordos Basin. Various kinds of gas accumulations have been discovered in the Majiagou Formation, each with differing scales of enrichment. However, the factors contributing to these differences remain unclear, thereby hindering the strategic deployment of regional exploration. In light of recent exploration advancements, this paper explores the reservoir-forming conditions in this area, comparing the accumulation differences in gas reservoirs of varying test productivity within the Majiagou Formation. Through an integrated study on source rock conditions and reservoir types and distribution, it has been concluded that two accumulation assemblages have been developed in the Fuxian area: the weathering crust and the interior dolomite. The weathering crust gas reservoir is primarily developed in areas where thick source and excellent reservoirs are efficiently matched, with palaeogeomorphology controlling the gas accumulation. Meanwhile, the interior dolomite gas reservoir mostly develops around the trench near the source or the fault-riddled area. A source rock of certain thickness found in the upper Paleozoic coal measure strata forms the base of gas accumulation, while the excellent aluminaceous mudstone cap in the Benxi Formation provides a stable condition for gas accumulation in the weathering crust reservoir. The favorable palaeogeomorphic position of the preCarboniferous period is the key factor controlling the reservoir quality of the Majiagou Formation. The high part of the palaeogeomorphology is a favorable area for the development of weathering crust reservoir, whereas the inner dolomite reservoir is locally developed in lower areas such as grooves. Furthermore, faults can effectively boost local gas accumulation. The research has identified the main controlling factors of the Ordovician natural gas reservoir in the area, which has guiding significance for the exploration and expansion from the core area to the outer and deeper layers in this region.