Abstract:  Bachu-Maigaiti area is an important focus area of oil and gas. In the Ordovician Yingshan Formation in well Yubei 1, industrial oil and gas flows of marine facies have been tested for 25.2 m³/d. It is urgent to solve the problem whether the crude oils from Ordovician of Yubei area and Bashituo oil field are of the same sources. Through the geochemical analysis, oil/ oil and oil/ source correlations of the crude oils from well Yubei 1 and Bashituo oil field, compared with the Ordovician crude oils from Tahe area, the geochemical characteristics of crude oil and oil source of the main oil-and-gas reservoirs in Bachu-Maigaiti area are discussed. The geochemical features of the Ordovician crude oils from Yubei area are similar to those of the Ordovician crude oils from Tahe area. According to the organic analogy of oil source, the Ordovician crude oils from Yubei area may originate from the Middle and Lower Ordovician source rocks of slope facies in the southwestern Tahe area. The light oils from Bashituo area mainly come from the Cambrian source rocks of basin-shelf facies, and partially from the Carboniferous source rocks of marine-terrigenous facies.