Abstract: Wangji Oilfield is an oilfield which has been put into development. By studying on the fault series of grabens, nose, the characteristics of sedimentary facies and the reflection characteristics of seismic profiles in Wangji area, the authors suggest a new cognition that the master tectonic of Wangji Oilfield is in fact a mud diapiric structure. This cognition will have practical significance to the study of reservoir distributive regularity and further exploration and development in Wangji Oilfield.