Abstract: The development of low temperature high Reynolds number wind tunnel has important strategic significance and engineering application value for China's defense industry. By means of liquid nitrogen injection, the first cooling system for continuous high speed wind tunnels has been built in China. The overall scheme and main technical indicators of the liquid nitrogen injection cooling system in the NF-6 continuous wind tunnel are introduced. The structure and technical principle of gas allocation operation of the cooling system are expounded and the debugging results are presented. The test results indicate that our calculation method of the liquid nitrogen consumption is correct and the liquid nitrogen storage device runs smoothly. The liquid nitrogen storage and ability of the driven gas can meet the requirements of low temperature wind tunnel experiment. The design of the gas allocation operation system is reasonable and the pre-pressurizing device works fine. The pressure control inside the tank and nozzle is stable. The gas allocation operation system has a good match with the whole cooling system. Throughout the debugging process, the key indicators such as the total temperature, total pressure, Mach number and running time have reached the design requirements. The experimental Reynolds number of the NF-6 continuous wind tunnel is improved by 50%.