The invention discloses a geometric figure simplification method for a BIM model. The geometric figure simplification method comprises the following steps: 1, acquiring surface geometric data of a BIMmodel body; 2, judging whether a certain grid surface of the BIM model is a triangular surface or not; judging whether the grid is a triangular patch or not according to the number of vertexes of a certain grid of the BIM model; when the polygon is a triangular surface, carrying out triangular patch merging simplification on the polygon, and then carrying out boundary line simplification on the merged polygon by adopting a three-point method; 3, according to a short edge principle, moving a point deleted after simplifying the boundary line of the polygon to the other vertex of the short edgein the adjacent edges; and 4, according to the obtained material information, endowing the simplified model with corresponding material attributes according to grid division. According to the geometric figure simplification method, simplification of triangular patches and boundaries of geometric data of the BIM model can be quickly realized; and by judging the shapes after combination, the advantages of the original geometric figure characteristics of the BIM model can be reserved.