This paper deals with sedimentary characteristics of the upper of 3rd Member to the lower of 2nd Member of the Shahejie Formation in the Yonganzhen oilfield based on core observation, granulometric analysis, seismic and logging data in combination with the facies analysis of single wells and profiles. The results indicate that they belong to river delta and lacustrine facies. The river delta facies may be divided into delta plain and delta front subfacies. Olistostrome was developed in lacustrine facies. The space-time evolution and controlling factors of sandbodies are systematically studied. The distributary channel and distributary mouth bar microfacies are the best favorable reservoir sands in this area.