The invention relates to a method for establishing a complex geologic model quickly and belongs to the technical field of geologic modeling for exploration and development of oil and gas. The method is characterized by including the following steps that firstly, a three-dimensional database of grid points in a work area is established; secondly, initial normal vectors of the grid points are calculated; thirdly, corrected normal vectors of the grid points are calculated; fourthly, the grid points are chosen; fifthly, grid data, with the vertexes deleted, of a complex geologic body in the work area are subject to triangulation to generate a Delaunay triangulation network, and the geologic model is drawn. According to the method, operational data are reduced by deleting part vertexes under the condition that precision is not affected, and the simplified complex geologic model is drawn through the Delaunay triangulation network triangulation method; in this way, the problem of low modeling speed caused by massive data is solved, a grid model with large data is greatly simplified, and the purpose of increasing the modeling speed is achieved. The method has the advantages that the modeling speed is obviously increased, and the high-fidelity geologic model can be obtained.