Abstract: Due to poor understanding on sedimentary system and reservoir distribution,the reservoir in Qian-3 member north fault block of Wangchang oilfield has bad waterflood-ing effect and low recovery. Based on modern sedimentology theory,making full use of coring,drilling and logging data,the in-depth study of sedimentary characteristics has been carried out. In the end,the study area has been defined as a typical saline lake delta,and delta front subfacies as its main sub-facies. The established sedimentary facies model dia-gram will provide guidance for potential exploration and roll-ing development of existing wells.