Abstract: In order to simplify the design process of computer interlocking software and improve the design efficiency, this paper proposed a modular computer interlocking software design method. The equipment such as railway signal, track section and turnout was built into different program modules by using object-oriented. Using polymorphism and drawing statements, draging the corresponding program module of each equipment with the mouse, the paper implemented the drawing of the interlocking software representation layer, generated the station yard data structure of single chain table, and used recursive algorithm to search the route and complete the design of interlocking software. The design method proposed in this paper and the traditional design method were applied to the interlocking software design of a station. The design process and design time of the two methods were compared. The total time of the design method proposed in this paper was saved by about 30% and the design efficiency was improved.