Abstract: The Dongwu Movement caused the exposure of Maokou limestone on the earth's surface and made it experience the supergene weathering process. Drilling reveals that the gas reservoir is closely related to the location and intensity of ancient landforms. Palaeogeomorphology is the main factor that affects the development and distribution of ancient karst. Southeastern Sichuan basin has had less drilling and is unevenly distributed, with insufficient exploration. Combining drilling with seismic survey, the authors exquisitely restored ancient karst landform of Maokou by applying the impression method and the residual method. A comparison of these two methods show that both methods can recover the same basic trend palaeogeomorphology. According to the geological features and practical data of the study area, the authors hold that the impression method has higher reliability. Based on an analysis of the ancient water system, the authors divided the study area into karst highland, karst slope and karst basin by combining it with paleogeologic map and drilling. The NW-SE trending karst highland in the southwest of the study area has the same highland as the karst highland in Shunan area, but it is higher than Shunan area. The groundwater runoff and corrosion holes of the karst slope area make it a favorable area for karst exploration.