The invention discloses a block segmentation method for a triangular grid model. The method comprises the steps of reading the triangular grid model and establishing topological information; calculating a concave-convex signal of a vertex of the triangular grid model and performing global Laplace smooth denoising; calculating standardized concave-convex information to obtain a concave characteristic region of the grid model; calculating normalized concave-convex information and reducing the concave characteristic region; extracting a center line of the reduced concave characteristic region; constructing a closed segmentation line by adopting a sector probe ray algorithm; optimizing the segmentation line by adopting a three-dimensional snake method and performing fitting and smoothing on the segmentation line; and segmenting the triangular grid model by adopting a regional growth method. According to the method, the segmentation line meeting a minimum principle in the triangular grid model is extracted for efficiently and reliably segmenting the model into minimum rule sub-blocks meeting the visual requirements.