Train communication system (TCMS) for CRH5 can realize real-time monitor and control on train traction, brake, power supply, air-conditioning, door control, bogie, and such subsystem and equipment. It can also identify train formation automatically and support real-time diagnosis technology, realizing data exchange between train and ground. Coupled with ground expert system, it is able to carry out statistic analysis on operation performance of onboard equipments. This improves operational efficiency of maintenance and vehicle wiring, assisting in reduction of dead weight.