An auxiliary device for determining a train position, wherein the auxiliary device comprises a core processing unit, a speed and distance unit, a trackside information receiving unit and a recording unit, wherein the speed and distance unit is configured to measure a speed and a distance of a train; the trackside information receiving unit is configured to receive trackside information; and the core processing unit monitors a power-on condition of a train position determining device in real time, and, if the train position determining device is determined to be in the power-on state switches the auxiliary device for determining a train position into a sleep state, or, if the train position determining device is determined to be in a power-off state, switches the auxiliary device for determining a train position into an operating state and continuously monitors a state of the train in real time when the train position determining device is in the power-off state by calculating, based on information from the train position determining device, output information of the speed and distance unit and output information of the trackside information receiving unit, whether or not the train moves, a moving direction, a moving distance and whether or not the trackside information is received, and stores a calculation result in the recording unit. the speed and distance unit is configured to measure a speed and a distance of a train; the trackside information receiving unit is configured to receive trackside information; and the core processing unit monitors a power-on condition of a train position determining device in real time, and, if the train position determining device is determined to be in the power-on state switches the auxiliary device for determining a train position into a sleep state, or, if the train position determining device is determined to be in a power-off state, switches the auxiliary device for determining a train position into an operating state and continuously monitors a state of the train in real time when the train position determining device is in the power-off state by calculating, based on information from the train position determining device, output information of the speed and distance unit and output information of the trackside information receiving unit, whether or not the train moves, a moving direction, a moving distance and whether or not the trackside information is received, and stores a calculation result in the recording unit. if the train position determining device is determined to be in the power-on state switches the auxiliary device for determining a train position into a sleep state, or, if the train position determining device is determined to be in a power-off state, switches the auxiliary device for determining a train position into an operating state and continuously monitors a state of the train in real time when the train position determining device is in the power-off state by calculating, based on information from the train position determining device, output information of the speed and distance unit and output information of the trackside information receiving unit, whether or not the train moves, a moving direction, a moving distance and whether or not the trackside information is received, and stores a calculation result in the recording unit. <EOS>