The invention provides a liquid nitrogen storage device for a continuous high-speed wind tunnel cooling system, consisting of a liquid nitrogen storage tank and an external pipeline. The total volume of the liquid nitrogen storage tank meets the demand of liquid nitrogen flow under the stable operation condition of the continuous high-speed wind tunnel, and meets the requirements for liquid nitrogen demand in the continuous high-speed wind tunnel preparation and transition processes. The external pipeline is composed of a combined filling system, a self-pressurizing system, a storage tank safety system, a storage tank gas supply system and an instrument monitoring system. The combined filling system is used for supplying liquid in the storage tank. The self-pressurizing system is used for cleaning, precooling and filling a main pipeline. The storage tank safety system is used for protecting an inner container from being destroyed by overpressure. The storage tank gas supply system is used for connecting with an external carburettor and a cryopump. The instrument monitoring system is used for matching with a liquid level parallel table on the liquid nitrogen storage tank so as to achieve real-time monitoring of the liquid nitrogen liquid level in the storage tank. The liquid nitrogen storage device for the continuous high-speed wind tunnel cooling system supports the construction of the first set of the continuous high-speed wind tunnel cooling system at domestic.