Abstract: Bouguer gravity anomaly is constantly correlated with terrain in mountainous areas, which is unserviceable to geological interpretation of gravity data. This phenomenon is mainly caused by inaccurate terrain correction density. We ascertain the terrain correction density in mountainous areas based on regression analysis. We obtain the terrain correction density by analyzing the relationship between the free-air gravity anomaly and the elevation, and modify the density according to the relationship between the calculated Bouguer gravity anomaly in each step and the elevation. Based on this, we adjust the terrain correction density of topographic correction successively until we obtain the optimum terrain correction density and the corresponding Bouguer gravity anomaly. We have adopted the proposed method for the terrain correction of the gravity data in the Jiuzongshan mountain and obtained the optimum terrain correction density after 5 iterations, and thus the Bouguer gravity anomaly was calculated. The results of Jiuzhongshan mountain confirmed the correctness of our proposed method.