PROBLEM TO BE SOLVED: To provide a train radio system that can reliably notify emergency of a base station from a mobile station.SOLUTION: The train radio system includes a base station M0, a first mobile station M2 and a second mobile station M2. The first mobile station includes a first transmitting part that transmits sub-tone signals to the base station so that the sub-tone signals are interposed at the time of transmission, and a detection part that detects a response signal to the sub-tone signals from the base station. The second mobile station includes a second transmitting part that secures wireless speech between the base station and the second mobile station by transmitting the sub-tone signal to the base station when the detection part can't detect the response signal.