Pressure swing adsorption nitrogen (PSA nitrogen) is an advanced gas separation equipment, which uses high-quality carbon molecular sieve (CMS) as adsorbent and PSA principle at room temperature to separate air to produce high-purity nitrogen. The diffusion speed of oxygen and nitrogen on the surface of zeolite is different. The diffusion speed of small diameter gas molecules (O2) is faster, and the micropores entering into carbon molecular sieve are more. The diffusion speed of large diameter molecule N2 is slower, and the micropores entering into carbon molecular sieve are less. Based on the difference of selective adsorption of carbon molecular sieve for nitrogen and oxygen, when compressed air passes through the carbon molecular sieve adsorption tower, oxygen adsorption is rich, nitrogen is rich, oxygen can be separated, and nitrogen can be produced continuously under PSA conditions.