NOVELTY - Preparing pure-oxygen gas and oxygen-depleted gas from oxygen-containing gas mixture by electrochemical process comprises using at least two water electrolysis units and a power supply unit corresponding to each water electrolysis unit, where the power supply unit comprises at least one hydrogen recycling power supply unit and an external power supply unit. The hydrogen recycling power supply unit uses hydrogen fuel cell. The external power supply unit uses solar battery, direct methanol fuel cell, and external AC main power supply. The water electrolysis unit is water electrolysis tank.    USE - The method is useful for preparing pure-oxygen gas and oxygen-depleted gas from oxygen-containing gas mixture by electrochemical method (claimed).    ADVANTAGE - The method: can stably and continuously produce high-purity oxygen (up to 95%) in a cost-effective manner in large indoor site or outdoor site; is suitable for large-scale industrial production; is safe and reliable; has high efficiency (more than 85%); utilizes device, which has long service life, compact structure, small volume and light weight; saves energy; and solves inflammable and explosive safety hidden troubles.    DETAILED DESCRIPTION - Preparing pure-oxygen gas and oxygen-depleted gas from oxygen-containing gas mixture by electrochemical method comprises using at least two water electrolysis units and a power supply unit corresponding to each water electrolysis unit, where the power supply unit comprises at least one hydrogen recycling power supply unit and an external power supply unit. The hydrogen recycling power supply unit uses hydrogen fuel cell. The external power supply unit uses solar battery, direct methanol fuel cell, and external AC main power supply. The water electrolysis unit is water electrolysis tank. Each power supply unit is respectively connected to an independent water electrolysis cell circuit. The hydrogen (FF) produced by the water electrolysis unit is collected into hydrogen pipeline and conveyed to a hydrogen fuel cell as a fuel. The oxygen produced in each of the water electrolysis unit is conveyed into an oxygen pipe to prepare pure oxygen. The hydrogen and oxygen containing mixed gas is conveyed respectively into cathode an anode of the hydrogen fuel battery energy of a power supply unit, conveying the hydrogen gas into the hydrogen gas cathode chamber of water electrolysis unit via a pipeline, and carrying out solid-liquid separation of the exhaust gas from the cathode side to discharge oxygen-depleted gas (DD).    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of the device for preparing pure-oxygen gas and oxygen-depleted gas from oxygen-containing gas mixture by electrochemical method (Drawing includes non-English language text).    Water (AA)    Air (BB)    Oxygen depleted air (DD)    Hydrogen (FF)    Gas liquid separator (HH)