"Digital Line Selection Platform in Design Phase of Railway" is an integrated design platform for railway line selection. On the railway line pre-feasibility study stage, a 3D line selection platform was established based on Digital Earth. Taking full advantage of Digital Earth's global digital terrain and high-definition video, it completed route planning and design. In the feasibility study and preliminary design stage, a generation line interactive visualization CAD systems was developed based on digital topographic maps and CAD. It can be used to complete the design, multi-line hub Line Plane design and Interchange transverse channel design, which covers various electoral line railway line digitization of content design. This article described the background, function and application of the application platform development and focused key technical issues in the development.