A computer assisted system for route selection of road is proposed based on the Geographic Information System(GIS). The function of the system includes the plan layout of route, longitudinal profile analysis, cross section analysis, comprehensive analysis of route, and printer and plotter output. The GIS data was input on the spot, from field records or from map digitization. The system was developed using XMGIS tool and C programming language. The system features data file selection, parameter setting, route layout and analysis, map drawing and table printing of route selection. The analysis, the design and the application method of the system are introduced. A mountainous forest road of 558m length is given as an example of route selection using the GIS-based route selection system. The application of the system reveals that the GIS-based technique is practical for route selection and road design. Its distinguishing feature in data storage, data analysis, route evaluation and route optimization will offer great help to road planning and road design.