The sixth member of Upper Triassic Yanchang Formation is the major exploration target zone in Dalugou area, Ordos Basin. Based on the outcrop observation, core description and logging analysis, the sedimentary systems, sedimentarymicrofacies and evolution ofUpper Triassic Yanchang Formation in Dalugou area are analyzed. The result shows that Chang 6 reservoir in Dalugou area mainly developed delta deposit system which includes delta plain facies and delta front facies. Distributary channel and subaqueous distributary channel sandstones are the skeletal sand bodies. In Chang 6 period, the sedimentary microfacies experienced delta front, delta plain to high curvature river of blending load. The distribution of the sedimentary microfacies of each sublayer of Chang 6 reservoir is studied. It is concluded that the hydrocarbon accumulation is controlled by sedimentary microfacies. The subaqueous distributary channel of delta front and distributary channel of delta plain are the most favorable facies belts for reservoir distribution and development.