The working principle of oxygen production of air separation is that according to the different boiling points of various gases in the air, it is pressurized, precooled, purified and liquefied by using most of the cooling capacity provided by the turbo expander, and then rectification is carried out to obtain the required oxygen / nitrogen products. The oxygen generation system of air separation includes air compressor system, precooling system, molecular sieve purification system, booster expander system, fractionator system, oxygen / nitrogen compressor system and pressure regulating station system.