Abstract:In modern rail transportation system, to ensure normal function of Multifunction Vehicle Bus(MVB)and Wire Train Bus(WTB) is the key to function test of the complete train. However, MVB employs the distributed network structure and source addressing broadcast mechanism, meantime WTB has the attenuation caused by long transmission path, both of which cause many problems in network debugging. Currently there is not much choice in debugging methods, which are all low in efficiency and require high technic skills from workers. Therefore, aiming at solving the difficulties in train debugging meanwhile meeting accuracy and timeliness requirements, an automatic test and diagnosis of MVB and WTB communication network tool is researched. This tool monitors the status of communication, positions the faulty points of MVB, and analyzes the waveform quality of WTB. In the research, the functions and working modes are studied; hardware modules including interface, data processing center and power, etc are designed; software layers and topology are defined. In the end, typical applications of the tool in high speed train and metro are exemplified.