Abstract: Through the analysis of the basic physical properties and geochemical characteristics of crude oil, combined with the drilling data, producing data and temperaturepressure testing data, the geochemical characteristics and hydrocarbon accumulation model of lower-middle Ordovician in No. 1 fault zone of Shunbei oilfield were studied. The results indicate the No. 1 fault zone of Shunbei oilfield is an unsaturated volatile reservoir with high gas-oil ratio and it was formed in the partial strong reduction sedimentary environment. The crude oil belongs to the marine crude oil which was formed by the evolution of the aprotic type Ⅰ kerogen. The marine crude oil generated is in the stage of high evolution and maturity. The biomarker of crude oil is similar to the black shale of Yultus, which is derived from Cambrian source rock. The migration path of oil and gas is dominated by vertical migration and the fracture is the main migration channel.