NOVELTY - A high-purity oxygen is prepared by cooling purified air in heat exchanger, feeding to bottom of pressure rectifying column, transferring heat and mass between bottom-to-top column plate or filler and up-to-down liquid inside the pressure rectifying column, over cooling the liquid air, and feeding to upper part of pressure rectifying column; extracting carbon dioxide (CO2), methane (CH4) and liquid air with low content of hydrocarbon and high content of oxygen from middle of pressure rectifying column as material for oxygen, throttling, and feeding into plate liquid air evaporator.    USE - Method of preparing high-purity oxygen (claimed).    ADVANTAGE - The method reduces energy consumption on high-purity liquid oxygen by 50%; is simple with high effect; and contributes to optimal economical benefit and lowest investment.    DETAILED DESCRIPTION - Preparation of high-purity oxygen involves:    (A) cooling purified air in heat exchanger, feeding to bottom of pressure rectifying column, transferring heat and mass between bottom-to-top column plate or filler and up-to-down liquid inside the pressure rectifying column, over cooling the liquid air at the bottom in heat exchanger, and feeding to upper part of pressure rectifying column;    (B) extracting CO2, CH4 and liquid air with low content of hydrocarbon and high content of oxygen from middle of pressure rectifying column as material for oxygen, throttling, feeding into plate liquid air evaporator, and feeding part of pressured nitrogen from upper part of pressure rectifying column into the plate liquid air heat exchanger to change heat with liquid air;    (C) extracting partial liquid air at sealed end of plate liquid air evaporator as the material for high-purity oxygen, feeding into high-purity oxygen column to rectify, evaporating the remaining liquid air, delivering into oxygen evaporator as heat source, condensing, rectifying into high-purity oxygen column, evaporating light component, and concentrating oxygen into high-purity oxygen; and    (D) feeding low-pressure gas from top of high-purity oxygen column into heat exchanger to reheat at normal temperature, and discharging.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic view for preparation of high-purity oxygen (Drawing includes non-English language text).