Abstract: This article analyzed the hardware structure and functional requirement for on-board equipment ATP of CTCS-1, established the use case model of the system. From the point of view of the system operation, the article divided the participants of the system function, defined the attributes and behaviors of the participants, thus established the scene class diagram model and the system class diagram model, described the interaction between participants of the system from different angles by using activity diagrams and sequence diagrams, finally, verified the functional models by using programming language.