A phenomenum of paragenesis of oil and trona (natural alkali, namely, NaHCO3 and Na2CO3·3NaHCO3) occurred in the Biyang Depression, Nan Xiang Basin in central China. The Nan-Xiang Basin was an evaporite basin during the Eogene, where the exploration proved certain scale oil and trona reserves. The crude oil could be divided into mature oil reserving in clastic reservoirs and immature (low mature) oil keeping in dolomite fractured and dissolved cavern reservoirs. Specially, the alkali layers were closely related to dolomites, namely, the wall rocks of the alkali deposits was these dolomites. There were similar geological conditions for the oil-trona paragenesis between the Biyang Depression and the Green River or the Uinta Basins in North America. The oil-trona paragenesis might be controlled by the tectono-paleogeomorphical evolution, paleogeography-paleogeoclimate situation, paleosedimentary environment, provenance and metallogenic material sources.