Abstract: Based on the analysis of geological background of 2 area of Tahe oil field,and combined with the development of Ordovician strata,studyed on the sedimentary environment and tectonic evolution,finded out the fundamental reason for the transformation of the Ordovician karst,application of rock thin sections,cathodoluminescence,carbonate mineral isotope analysis technology,it is concluded that the Ordovician rock slices dissolved pore wall existed the oxidation characteristics and terrigenous clastic;the fill material cathode luminous orange red etc that indicated the formation conditions of the strong oxidation;the carbonate mineral isotope indicated the atmospheric water medium;the comprehensive analysis showed that the Hercynian Early Ordovician karst environment is an open system of the continental crust of atmospheric water infiltration to the formation of karst environment transformation.Application of seismic data of single well restored the Ordovician top interface of karst landform,combined with karst terrain features,it concluded that the region near the region of northern karst slope was draining wa Dang transformation which was the most favorable area for oil and gas accumulation of mineral resources.