The balise is the basic information transmission equipment of the train control system. It has high precision and reliability when used for positioning. However, its core component, radio frequency identification (RFID) tags, is monopolized by foreign manufacturers. Therefore, a balise auxiliary positioning system based on long range radio (LoRa) is designed. The system uses the peak value of the received signal strength indication (RSSI) as the basis for judging the position of the train query to the balise, and obtains the accurate peak time of the RSSI value through the envelope and interpolation processing method. The time is combined with the mileage data of the odometer (ODO) to achieve accurate positioning. The experimental results show that the positioning accuracy of the system is 1.32 m, 2.15 m and 3.4 m respectively when the speed of the query is 15 km/h, 30 km/h and 60 km/h. The experimental results show that the positioning method proposed in this paper can realize the auxiliary positioning of the train, which provides a feasible technical scheme for the localization of the balise.