Sedimentary bauxite deposit in the northern part of China mainly locates in the sag of the touching area between Ordovician limestone and Carboniferous Benxi Group. For the reason that there is a density difference between the sides of the above touching region, the target areas can be located by the low bouguer gravity anomaly. However, due to the influence by the observation on undulated surface and by the difficulties in density selection when apply the middle layer and the terrain corrections, the bouguer gravity anomaly may appears several mirroring or positive correlative false anomalies regarding to the topography, which gives troubles to determine the target areas. In order to eliminate or weaken this false anomaly, we obtained a new gravity anomaly by using a potential field on curved surface processing method and a moving window regression analysis method, and reinterpret it. The results show that the false anomalies can be well eliminated in bouguer gravity anomaly by these two methods, and the undulating topography of the above touching area is correctly reflected, and the target areas is accurately determined, which helps to achieve the efficient prospecting purpose.