Abstract: 3D geological modeling is a 3D digital technology originating from computer graphics in the industrial field and later introduced into geoscience. The irregularity of geological mass, spatial heterogeneity of geological characteristics, sparsity of known parameters, and the iterative nature of the understanding process determine the special requirements for graphics geometry algorithms and rendering techniques in 3D geological modeling. These factors also determine the fundamental difference between 3D technologies in other fields such as GIS and BIM. In response to the reality that there is a wide variety of engineering geological 3D geological modeling technologies in China's infrastructure construction field, with varying levels of quality, this paper systematically expounds on the basic theory of 3D geological modeling, core technologies, modeling methods, application function implementation, and prospects:(1) 3D geological modeling is based on the theory of discrete mathematics, with interpolation algorithms being the most critical core technology. This paper introduces and compares two interpolation methods, discrete smoothing (DSI) and Kriging. It argues from the perspectives of principle and application that DSI has better adaptability. (2) Explicit and implicit modeling methods are the common methods of three-dimensional geological modeling formed by the core technology for different scenarios, which are suitable for geographical exploration and geophysical exploration in the field of engineering geology respectively. The paper illustrates the characteristics of each method with application cases. (3) Application functions are the ways in which explicit and implicit modeling methods are applied to geological bodies with different characteristics. The general-purpose functions are applicable to all geological bodies involved in geological fields such as strata and structures, while customized functions are aimed at specific geological masses concerned by the industry (such as the deep valley bank slope unloading belt in the hydropower industry) and the main purpose is to improve the modeling efficiency. By summarizing the stage of 3D geological modeling technology, this paper provides valuable technical guidance for future development and will provide important technical support for the transparent representation of 3D engineering geological body structure.