Benxi formation, Yanchang gas field in Ordos Basin, is rich in natural gas resources, but the sedimentary environment is complex, the lateral changes of sand bodies are rapid, and the continuity of gas reservoirs is poor. Exploring its sand body types and development models can provide useful reference for oil and gas exploration in this area. Based on core observation and logging data analysis, the characteristics of sedimentary microfacies in Benxi formation are studied. The results show that Benxi formation is a barrier coastal deposit, and three types of deposits can be further identified: barrier bar, lagoon and tidal delta. From west to east, the area shows the change law of lagoon-barrier sand bar-shallow sea shelf. Barrier coast deposits were formed by wave and tidal transformation in the northern and southern deltas of the basin under the control of ancient uplift, and their evolution was mainly influenced by the central ancient uplift and climate. The research results are of theoretical and practical significance for perfecting the sedimentary model of coastal system affected by tides and predicting the distribution law of favorable reservoirs in barrier bar.