Abstract: Based on comprehensive analysis of mineralogy, grain sizes, sedimentary structure and depositional setting, the unit 6 - 10 of Es23 (middle 3rd member of Shahe-jie Fm) in Pucheng oilfield are determined to be subaqueous fans, where several microfacies, including channel, interchannel, sand sheet and debris flow, are recognized. The areal distribution of the microfacies has the characteristics of sector configuration. Based on analysis of single well microfacies and their areal distribution, depositional models of subaqueous fan in Es23 are built The genetic mechanism of subaqueous fan is discussed and it is believed that the formation of subaqueous fan is controlled by structure, depositional topography, climate and changes of base-level.