The invention provides a method for diagnosing real-time faults of a train, which comprises the following steps of: identifying state information of each traction process step through a state identification module during a traction process period of executing a traction force forming process by a train; receiving the state information through a service platform, and screening out a traction process step with a fault according to the state information and the traction process logic; and analyzing the fault tree corresponding to the traction process step with the fault, and obtaining a fault diagnosis result according to the fault logic of the fault tree. According to the method and system for diagnosing the real-time faults of a train, the real-time faults of a train can be checked under the traction process working condition, various faults related to train traction are involved, ground personnel can rapidly locate the faults, and a driver can conveniently conduct further operation. The processing time of train faults is shortened, and the influence of the faults on the train is reduced.