Abstract: Abstract: 【objective】 The surface structure and internal physical properties of geological bodies are simulated by using 3D geological modeling technology, which provides a reliable basis for revealing the spatial distribution of geological resources, resource estimation and resource development, and is the core technology of the construction of "glass earth". It is also an important carrier of geological time and space big data. Since the 1990s, 3D geological modeling technology has been developed rapidly. Researchers proposed many different modeling methods, but there were still many problems in fine modeling of complex orebodies. Compared with the implicit modeling method, the explicit modeling method was more accurate in depicting small-scale geological structure features. However, for the large-scale fine 3D modeling of geological bodies such as complex vein orebodies, there were still some problems, such as low modeling accuracy and poor morphological expression of the model, so it is difficult to meet the needs of mine production and resource estimation at present. 【Methods】 In this paper, aiming at a series of complex geological phenomena of local vein orebody, such as bifurcation compound, non-ore skylight, rock entrapment, fault cutting and so on, the techniques of orebody split line, segmented modeling and orebody suture are comprehensively used to construct orebody split line, segmented modeling, orebody suture and so on. Four kinds of explicit 3D modeling methods of complex vein orebody, such as bifurcation composite orebody, non-ore skylight orebody, stone-bearing orebody and fault cutting orebody are studied systematically. Among them, the constraint point is generally located in the ore center and the outline of the orebody, and the complex part of the model needs to add constraint points to complete the constraint of the shape of the orebody. The splitting line is the connecting line between the cusp-out point at both ends of the boundary line of the orebody and the central point of the ore-seeing project. it is mainly used to split the complex vein orebody, and the split line is used to model the branch-bifurcated composite orebody according to the regional geological law. Segmented modeling is to model the complex parts of complex orebodies separately. The stitching of orebody is to assemble the segmented model along the strike to form a complete model. 【Results and conclusion】 Through the above technology and the explicit modeling method based on measured data, the high-precision and fast 3D modeling of complex vein orebody is realized, and the difficult problem of narrow, thin and complex vein orebody modeling is solved effectively. The 3D modeling process of different complex vein orebodies is improved, and the orebody model is displayed in 3D space in multi-angle, and the most real geological shape of the orebody is reconstructed with the outline of the orebody. High-precision model will not only obtain detailed 3D information of orebody, but also will grasp the distribution law of orebody quickly and accurately. This modeling method is of great significance to the fine 3D modeling of rare and precious metal and other complex vein orebodies, the estimation of mineral resources and the formulation of mineral resources development and utilization plan, and will better guide the exploration and prospecting work.