Abstract: Through comprehensive analysis on core data,log- ging data and chemical experiment data,sedimentary fea- tures of the 6th oil layer of Yanchang formation and the distribution of sedimentary microfacies have been identi- fied.As glauconite of secondary mineral is found to be ex- isted in sandstone and siltstone,a suit of delta front sub- facies sandbodies,not the delta plain subfacies are consid- ered to be developed in the 6th oil layer of Yanchang for- mation.The delta front subfacies include river mouth bar, distal bar and tributary bay subfacies.On the basis of macro depositional setting,micro sedimentary features and evolution regularity of sedimentary facies,sedimenta- ry patterns of the research area have been established.