Abstract: The modern design of railway lines was with particular emphasis on the design of railway line scheme under complicated geological conditions and selection. The geological problems involve many factors so the railway line scheme of the decision making has the characteristic of strong comprehensiveness. By using the function of data management, spatial analysis and decision-making of GIS(Geographic Information System), it could be implemented the effective expression and extraction for bad geological characteristic of the regional railway lines scheme, analyzed the bad geological situation comparison between different railway lines. The article used ArcGIS to construct the analytic hierarchy process model of railway auxiliary decision-making in the bad geological area and implement the railway line selection based on the geological combined with the analytic hierarchy process.