Abstract: Based on the seismic and drilling data and combining with geological sections, the paper discusses the the structural geometry and the characteristics of movement of the transitional zone from Shawan sag to the western Well Pen-1 sag by using fault-related fold theories. The study shows that a paleohigh exists in the transitional zone, which exhibits a NW-SE trending, irregular strip. Based on which, through the structural model establishment of the transitional zone from Shawan sag to the western Well Pen-1 sag, it is considered that the basement of the paleohigh had a pattern of “uplift plus semi-graben” and was controlled by both back-thrust reverse basement fault and extensional normal fault, and changed to a pattern of “sole uplift” after the Middle Permian. The forming process of the paleohigh can be divided into 5 periods such as the prototype period from the Late Carboniferous to Early Permian, the development period at the early Middle Permian, the peak period at the late Middle Permian, the inherited period from the Late Permian to Middle Jurassic and the reconstruction period from the end of the Middle Jurassic up to now