Abstract:The large-scale migration of surface water reserves will cause surface deformation in the surrounding area, and cause geological disasters in severe cases. Therefore, the monitoring and prediction of surface deformation is of great significance. Aiming at this phenomenon, a method based on spherical harmonic transformation and load response theory is proposed to solve the three-dimensional surface deformation caused by the large change of water body. When simulating a load model with a water body as the center of mass, a grid matrix of average water thickness is created based on the DEM data of the study area, and its spatial resolution can be accurate to about 1.1km. Based on the load response theory, the average water thickness grid matrix is expanded in spherical harmonics. By retaining the higher-order harmonic information, a more accurate three-dimensional surface deformation and its time series can be calculated. Taking the Three Gorges Reservoir as an example, the error rate of the equivalent water height in the inversion process can be reduced to 0.742%, and the trend of the vertical deformation time series is in good agreement with the results of the load Green method.