The invention discloses a method for building the model of a substation grading ring based on point cloud data, wherein the grading ring comprises at least two rings. The method includes following steps that: (1) the point cloud data of the substation grading ring are collected through a plurality of times of scanning; (2) the point cloud data of the substation grading ring which are collected through the plurality of times of scanning are spliced; (3) de-noising processing is performed on the point cloud data; (4) sparsification is performed on the de-noised point cloud data; (5) the point cloud data of the grading ring are segmented into ring point cloud data and connecting component point cloud data according to the curvature information and structural features of the point cloud data; (6) the models of at least two rings are built based on the ring point cloud data which are obtained through segmentation, a connecting component model is built according to the connecting component point cloud data which are obtained through segmentation; and (7) the rings and the connecting component are spliced together, so that a complete grading ring model can be obtained. With the method of the invention adopted, the model of the substation grading ring can be built accurately and efficiently, and a solid foundation can be provided for three-dimensional, visual and intelligent monitoring of a substation.