The invention provides a power transmission line geological stability evaluation method supported by a GIS. The problem to be solved by the invention is how to carry out power transmission line geological evaluation by using spatial analysis data of a GIS. The main technical points are as follows: establishing a geological stability evaluation index system; empowering influence factors; constructing an evaluation model; reading GIS environment analysis data, and carrying out geological stability analysis through rasterized data, that is to say, preprocessing data of the geological stability analysis; carrying out power transmission line geological stability analysis by means of the data of the geological stability analysis. The advantages of the method are that the data processing and spatial analysis functions of the GIS are fully utilized to realize processing (value assignment, empowerment, classification, etc.) of data of various power transmission line geological stability influence factors and realize superposition analysis of the influence factors, so geological stability values are extracted and obtained. Experiments show that the method is different from conventional powertransmission line selection methods.