Abstract: Aiming at the low efficiency of route search in interlocking system, this paper analyzed the limitations of breadth first, A * and other search algorithms, put forward a Depth First Search (DFS) route search algorithm with constraint conditions, built station type topological network, dynamically created binary tree model, designed the program flow of improving DFS route search algorithm. From the teaching point of view, the paper proposed the software design scheme, developed the software on the platform of Visual Studio 2010, implemented the design of interlocking simulation teaching system in CTCS-3 Train Control System, which not only had good operability, but also integrated the functions of fault setting, communication data package inquiry, etc.