A device for extracting medical or industrial oxygen from the air by deep freezing. The process adopts the deep freezing cycle principle of low-pressure turbo expander to make the air into liquid state, and then rectifies in the fractionator according to the boiling point of liquid oxygen and liquid nitrogen, so as to obtain more than 99.6% of industrial or medical oxygen. The liquid oxygen is compressed to 15MPa by the liquid oxygen pump, gasified and recovered, and then filled into bottles for use.Air Separation Plant Made in China website:http://www.cryoseparation.com/air-separation-plant/