The Ordovician in Gucheng area of Tarim Basin has shown good exploration potential in recent years. Based on observation of the core and petrographic thin section, analysis of cathodoluminescence, inclusion and bitumen reflectance of more than 10 Ordovician exploration wells, and interpretation of seismic data in Gucheng area, and combined with regional research results, the reservoir forming and hydrocarbon accumulating conditions of Ordovician carbonate rocks in Gucheng area are systematically analyzed. The results show that: (1) Paleostructure-geofluid processes is an important factor controlling the development of granular dolomite reservoir and hydrocarbon accumulation in the lower member of Yingshan Formation and Penglaiba Formation of Lower Ordovician. (2) Tectonic thermal events after Permian played a key role in adjustment and transformation of oil and gas accumulation. Under the influence of magmatic hydrothermal activity, large-scale oil cracking of primary reservoir occurred in Caledonian-Early Hercynian period, forming crude oil-cracked gas reservoirs and residual paleo reservoirs. (3) The formation and evolution of Ordovician oil and gas reservoirs have experienced three stages, including the formation of primary oil and gas reservoirs, the destruction of ancient reservoirs and the generation of oil-cracked gas, and the adjustment, destruction and reformation of gas reservoirs. It is pointed out that the west and the north of Gucheng low uplift are favorable for oil and gas exploration because of good combination conditions of source, reservoir and caprock, and less influence of faults and magmatic intrusion.