Abstract: Chang 8 member of Yanchang Formation is the major reservoir in Jiyuan Oilfield. With the development of oil and gas exploration, the areal heterogeneity of the reservoir has become an obstacle for further exploration and development, so the fine sedimentary facies description is particularly significant. Based on the analysis of sediment provenance and facies indicator, it is considered that Chang 8 member of Yanchang Formation is controlled by the provenances from the northwest and northeast, experienced the transformation from delta plain to delta front, and deposited distributary channel sand body which is superimposed vertically and continuous laterally. The physical properties of Chang 81 layer under different subfacies and different sources are contrasted. The result shows that the reservoir property of delta plain in Chang 8layer is better than that of delta front, and the reservoir property controlled by the provenance from northwest is better than that controlled by the provenance from the northeast. The favorable reservoirs of Chang 8 member are predicted, and it is considered that the reservoir in the northwest of Jiyuan Oilfield has great hydrocarbon potential.