To obtain the positive height or normal height of a point by GPS measurement, it is necessary to know the geoid difference or elevation anomaly of a point. The accuracy of geoid difference or elevation anomaly determines the accuracy of GPS leveling. In this paper, EGM96 model is used to calculate the height anomaly. When fitting the regional quasi-geoid model with the elevation anomaly of known leveling points, the part calculated by EGM96 model should be excluded first. Then the remaining elevation anomalies are fitted and interpolated, and the removed part is restored by EGM96 model at the interpolation point to obtain the elevation anomalies at this point. The calculation of GPS leveling of a line shows that the accuracy of fitting elevation with EGM96 model is not improved much. However, for large-scale measurement, this method is expected to improve the fitting accuracy of GPS leveling. Thank you for your adoption.