Abstract: In view of the uncertainty between fault types and symptoms in ZPW-2000A track circuit state evaluation and diagnosis, set pair analysis and membership function are introduced into track circuit state evaluation and fault diagnosis. Firstly, the collected data are processed and the relationship between fault type and fault symptom is analyzed, and the fault type set is established. Secondly, set pair analysis is used to establish the relationship between the fault type and the running state of the track circuit, and entropy weight method is used to combine with set pair analysis to determine the accurate weight value between the symptoms. Finally, the membership function in fuzzy theory is used to describe the corresponding relationship between the operation state and the state level, and a matrix model of the same fault type and different fault type is constructed. The simulation results show that the evaluation method based on set pair analysis and membership function can effectively reflect the operation state and fault type of track circuit.