The invention discloses a station relay and a data transmitting method thereof, and belongs to the technical field of railway wireless communication. The technical problem that an existing relay server cannot monitor the station relay in real time easily is solved. The data transmitting method of the station relay comprises the steps that first legal data sent by a train tail device are received; whether the first legal data are train tail information data or not is judged; if not, the first legal data are directly sent to the relay server; if yes, the train tail information data are written into a data file, and the train tail information data of the data file are uploaded to the relay server.