Disclosed are method and apparatus for obtaining residual gravity anomaly. The method comprises obtaining Bouguer gravity anomaly of a target region, determining a first pre-set range corresponding to each sampling point in the target region, obtaining a first regional field value of each sampling point in the first pre-set range through a surface fitting method based on the coordinate and field value of the sampling point, traversing the target region to obtain first regional gravity anomaly of the target region according to the first regional field values of the sampling points in the target region, and obtaining first residual gravity anomaly of the target region according to the Bouguer gravity anomaly and the first regional gravity anomaly. The residual gravity anomaly thus obtained is more accurate, thus enabling an accurate prediction of an underground geological body.