The invention discloses an automatic replenishment method and system for vehicle-mounted dewar liquid nitrogen of a superconduction magnetic levitation vehicle. The system comprises at least two sensors, a controller, a self-pressure-boosting liquid nitrogen storage tank, a main electromagnetic valve, a plurality of secondary electromagnetic valves and an exhaust valve; the sensors are arranged at the top and the bottom of the interior of each container filled with the liquid nitrogen and are used for measuring the temperature; the controller is connected with the sensors, the main electromagnetic valve, the secondary electromagnetic valves and the exhaust valve; the self-pressure-boosting liquid nitrogen storage tank is connected with the main electromagnetic valve; the main electromagnetic valve is further connected with all the secondary electromagnetic valves and the exhaust valve; and all the secondary electromagnetic valves are connected with the corresponding containers filled with the liquid nitrogen. By means of the automatic replenishment method and system for the vehicle-mounted dewar liquid nitrogen of the superconduction magnetic levitation vehicle, real-time control over the liquid level of existing vehicle-mounted dewar liquid nitrogen and full-automatic filling of the liquid nitrogen can be achieved, time is better saved, manpower is better saved, and more efficient running operation is better carried out.