The invention discloses an automatic completion planar graph drawing method based on three-dimensional point cloud. By adopting the automatic completion planar graph drawing method, a completion planar graph can be automatically drawn according to heights of floors of expected planar graphs through three-dimensional point cloud data processing, the method has two advantages, namely, on the one hand, characteristic extraction on three-dimensional point cloud of buildings is avoided, two-dimensional point cloud is subjected to linear fitting through least square fit directly, the working difficulties are reduced, and the graph precision is improved; and on the other hand, the planar graph is automatically fitted and drawn, so that the working efficiency is greatly improved.