With the rapid growth of the national economy, the demand for electricity is increasing rapidly. In order to ensure electric power system operates safely and stably, much attention has been paid to insulation condition and lightning proof abilities of HV transmission lines. Nowadays the study of lightning protection of transmission line, which takes districts as the research object, has certain limitations. To provide a more rational basis for insulation design of the new transmission lines as well as insulation improvement in the old, this paper brings in a new analysis method based on ArcGIS. It is also taking the environmental factors, such as landscape along the transmission lines, into consideration. This method first filters and statistically analyzes lightning location data, and establishes assessment model of lightning proof abilities of transmission lines, which can serve as reference for finding the segment struck by lightning. In order to verify the feasibility of the model, this paper took a 220kV transmission line of a region in the Pearl River Delta as an example, and analyzed the distribution of parameters of lightning activities for the past decade. The result shows that the segments where flashover trip occurred have great relevance with the results of the data analysis. It is true that the model can be provided as a reference to the improvement of the insulation level of lines.