The invention discloses a method for protecting the copyright of a 3D model of a geologic body based on digital watermarking technology. The method includes the following steps: firstly, conducting PCA analysis on a point cloud model of a geologic body; also decomposing the point cloud model of the geologic body by using an octree structure to obtain a plurality of large block models, then based on a search Ellipsoid algorithm of a KD-Tree index structure, determining the neighborhood relation among sampling points in each block model; resolving an adjacent matrix through the neighborhood relation, obtaining a corresponding stiffness matrix, and further obtaining a Laplace matrix; decomposing the Laplace matrix to obtain the feature value and the feature vector of a corresponding matrix, and obtaining the frequency spectrum information of each block model in combination with model length data of the sampling points; analyzing the frequency domain information by conducting mathematical statistics to obtain the one digit digital watermarking of each block model, using the procedure to generate a digital watermarking sequence of the entire model; and finally using related coefficients to determine the related degree between the digital watermarking information which is registered in an authority database and the watermarking information which is generated by the 3D model of the geologic body through the procedure so as to determine the copyright of the 3D model of the geologic body.