Oxygen and Nitrogen separation system is the core part of air separation of Liquid Nitrogen Plants. Its main body is two adsorption towers filled with carbon molecular sieve. When clean compressed air enters an adsorption tower, O2, CO2 and trace H2O are adsorbed by carbon molecular sieve, and nitrogen is output from the outlet to the product nitrogen. When one tower is in the process of adsorption nitrogen production, the other tower can discharge O2, CO2 and H2O adsorbed in the molecular sieve from the micropore by reducing pressure, so as to achieve regeneration and desorption of the molecular sieve. The two towers are adsorbed and regenerated alternately, producing nitrogen continuously. The oxygen nitrogen separation system is composed of adsorption tower, carbon molecular sieve filled in the tower, pneumatic valve, muffler, throttle valve, compression cylinder, pressure gauge and so on.