Because the air contains a certain amount of water and oil vapor, the oil vapor is easy to be adsorbed by the carbon molecular sieve and difficult to desorb without strict air purification treatment after passing through the compressor. The pore size of the carbon molecular sieve in the nitrogen generator is filled, resulting in the carbon molecular sieve "poisoning" failure in the nitrogen generator. Therefore, it is necessary to set up strict air purification device before compressed air enters the nitrogen generator adsorption tower, which is an essential part to ensure the service life of carbon molecular sieve of nitrogen making machine. Although water is not fatal to the carbon molecular sieve of nitrogen generator, it will increase the adsorption load of carbon molecular sieve of nitrogen generator, that is, it will affect the capacity of nitrogen making machine to absorb O2 and CO2. Therefore, drying and removing water by compressed air is an important problem to improve the adsorption capacity and stability of carbon molecular sieve of nitrogen making machine.