TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The alternating procedure comprises performing middle temperature alternating reaction to carbon monoxide in first target gas flow at 300-500 degrees C; and reducing temperature of gas flow after performing middle temperature alternating reaction to 180-260 degrees C, and performing low temperature alternating reaction to obtain second target gas flow. The first target gas flow in alternating procedure is 4.0-10.0 MPa. The working pressure of methanol synthesis purge gas flow in first film separating procedure is 5.0-27.0 MPa. The second film separating procedure comprises contacting third target gas flow with first sectional film separating component to separate; and contacting non-permeable gas obtained from first sectional film separating step with sectional film separating component to separate, where permeable gas of first sectional film separating step and permeable gas of second sectional film separating step are compressed and mixed to form second hydrogen rich gas flow, and non-permeable gas in second sectional film separating step forms fourth target gas flow. The decarbonizing solvent in decarbonizing procedure is methyldiethanolamine (MDEA) solution. An INDEPENDENT CLAIM is included for a processing device which comprises first film separating device, which is at least provided with one film separating component, and one non-permeable side of film separating component is connected with carbon monoxide alternating device. The carbon monoxide alternating device comprises at least one alternating tower, where discharging end of alternating tower is connected with decarbonizing device. The decarbonizing device comprises at least one absorbing tower, where discharging opening of absorbing tower is connected with purified gas separator. The gas phase outlet of purified gas separator is connected with purified gas absorber. The processing device further comprises second film separating device connected with discharging opening of purified gas absorber, where second film separating device is provided with at least one film separating component.