Abstract: In 3D geological modeling, the existing geological sealed block recognition algorithms were based on topology between cells of geological surfaces. These algorithms faced some obvious weaknesses such as topology data redundancy and high computational complexity. To solve these problems, with research objective of recognizing topological closed 3D geological blocks, this paper presented a topology model that is suitable for expressing complex topological relationship between geological surfaces to separate geometry and topology of geological surfaces, and proposed a rapid construction process of this model. Geological sealed block is area surrounded by geological surfaces that are topological closed in the underground space; therefore, geological sealed block recognition is a topological problem in essence, not relating to geometry. From the perspective of this point, the defined topology model include topological node, topological border, topological facet, topological surface, and topological block. Its construction process follows four steps: search topological node in geological surfaces boundary; construct topological border; build topological facet composed of closed topological borders; search topological block in all topological facets. When searching geological sealed blocks, the built topology model transfers searching process from geometric space to topological space. The rapid construction process due to the only use of boundary information of geological surfaces during construction process of the topology model. Experimental results show that this algorithm has a good performance of time complexity and can satisfy all kinds of relationship between complex geological surfaces because of the integrity of topology model in theory.