Abstract: Aiming at the problems of staircase effect and physical property distortion caused by regular grid discretization and constant density assumption in traditional terrain correction for gravity exploration, this study proposes a high-precision terrain correction method integrating adaptive mesh generation and a 3D spatially variable density model. Firstly, taking terrain slope and roughness as characteristic criteria, the adaptive triangular mesh algorithm is adopted to realize refined discretization of complex surface topography, balancing fitting accuracy and computational efficiency. Secondly, a continuously differentiable 3D spatially variable density model is constructed using the inverse distance weighting method and radial basis functions. Finally, the forward calculation of variable-density elements is realized combined with the polyhedral gravitational field theory. Model experiments show that the root-mean-square error of the proposed method is significantly superior to those of traditional regular grid and conventional irregular grid methods, providing a reliable technical solution for high-precision gravity data processing under complex geological conditions.