Abstract: The types of microfacies, characteristics of planar distribution and evolution of sedimentary have been systematically analyzed based on the observation of cores, well logging and analysis assay data. The conclusions show that the study area of Dong 3 interval is comprised by meandering river, mainly developed channel and flood subfacies, the types of microfacies are channe fill, point bar and flood plain. With obvious bifurcation and confluence phenomenon, channel sand body controlled by the river presents a bending strip distribution. Point bar is developed in the river inturn and flood plain is area distributed in the lateral of river. The river has evolved from channel's incision, lateral accretion to the flood plain. And the conclusions also show that the lateral margin of channel body and the top of point bar, matched with the slope structure background are favour of forming lithological and litho-structural reservoir.