The invention discloses a triangular prism-shaped geological model construction method. The method includes the following steps: (1) a model projection region is set and divided into planar grid units, and nodes in a model bottom control region are divided into nodes inside the control region, nodes outside the control region and nodes on the control boundary; (2) each layer of geological materials are divided into a grid layer, whether the nodes are located on the boundary surface of the materials of the layer is judged, the coordinates of the nodes of the materials of the layer higher than the boundary surface of the layer are vertically moved down to the boundary surface of the materials, the nodes of each layer are numbered, and the control boundary and the region interior are specially processed; (3) triangular prism units k, l, m, k plus np0, 1 plus np0 and m plus np0 are sequentially constructed on virtual nodes corresponding to the ith layer and the i plus 1th layer until the ground surface; (4) real node numbering is carried out on the nodes from the first layer, whether the nodes are superposed with the corresponding nodes of the lower layer is judged, if so, then the nodes are numbered by adopting the corresponding real nodes of the lower layer, or else the nodes are new real nodes; and real node numbering is carried out; (5) the virtual nodes forming the units are replaced by the real nodes, and thereby a geological model is generated.