The invention discloses a method for measuring level elevation difference by using a terrain correction-based gravity field model. The method includes the following steps that: a GNSS (Global Navigation Satellite System) static measurement method is adopted to observe each control point in a measurement area; collected GNSS data are processed, after non-constrained adjustment is carried out, so that the geodetic coordinates and geodetic elevation difference of the control points are obtained; an EGM2008 gravity field model is used to calculate the elevation anomalies of each control point according to the geodetic coordinates of the control points obtained in the step two; with the influence of terrain fluctuation considered, the elevation anomalies calculated in the third step is corrected, so that elevation anomalies with higher precision can be obtained; and level elevation difference is calculated according to the geodetic elevation difference calculated in the step 2 and the elevation anomalies of the points calculated in the step 4. Compared with a geometric level measurement method, the method has higher measurement efficiency. With the method adopted, the accuracy of the measured level elevation difference can satisfy the requirement of three-class level measurement; and the elevation measurement and GNSS plane measurement of three-dimensional control points can be performed synchronously, and additional field observation is not required.