Using liquid ammonia as raw material, after ammonia is cracked, 2.64Nm3 mixed gas can be obtained per kilogram of liquid ammonia cracking, which contains 75% hydrogen and 25% nitrogen. The obtained gas contains less impurities (the water vapor in the impurities is about 2 g/m3, and the residual ammonia is about 1000ppm). After passing through the molecular sieve (UOP) adsorption purifier, the dew point of the gas can be reduced to below -600C, and the residual ammonia can be reduced. to below 3PPM. Ammonia cracking hydrogen production furnace can be used for bright annealing of non-ferrous metals, silicon steel, chromium steel and stainless steel and other metal materials and parts, decarburization treatment of silicon steel sheets, copper-based, iron-based powder metallurgy sintering, hydrogen burning treatment of metal parts of electric vacuum devices , Protection sintering and sealing of semiconductor devices, raw material gas for palladium alloy membrane diffusion and purification of hydrogen, etc. The raw material ammonia is easy to obtain, the price is low, and the raw material consumption is less. Ammonia cracking to produce protective gas has the advantages of low investment, small volume and high efficiency.