NOVELTY - Separating carbonyl composite feed gas comprises obtaining carbon monoxide (CO) product gas (14) and H2 feed gas (24); obtaining hydrogen (H2) product gas (18) and normal pressure desorbing gas (19), further separating to obtain CO enrichment gas (21) and permeable gas (22) rich in H2; and pressure-changing.    USE - The method and system are useful for separating carbonyl composite feed gas and separating CO and H2 in the coal gas, natural gas, light oil, pyrolysis gas, coke-oven gas, calcium carbide tail gas, yellow phosphorus tail gas and other carbonyl composite feed gas (all claimed).    ADVANTAGE - The energy consumption of the compressor is completely provided with 35 percent of the pressure-changing absorbing technology; cover an area of not more than 15 percent of the complete pressure-changing absorbing technology; and the total investment not more than 70 percent of the complete pressure-changing absorbing technology. The method is fit for the separation of CO and H2 in the coal gas, natural gas, light oil, pyrolysis gas, coke-oven gas, calcium carbide tail gas, yellow phosphorus tail gas and other carbonyl composite feed gas.    DETAILED DESCRIPTION - Separating carbonyl composite feed gas comprises: entering the CO separating ice chest (4) to obtaining the CO product gas (14) and H2 feed gas (24) after the washing the carbonyl composite feed gas by the low temperature methanol and processing by molecular sieve; H2 feed gas (24) entering the pressure-changing, absorbing and hydrogenizing unit (6), separating to obtain the H2 product gas (18) and the normal pressure desorbing gas (19); the normal pressure desorbing gas (19) entering the film separating unit (8) again, further separating to obtain the CO enrichment gas (21) and permeable gas (22) rich in H2; and CO enrichment gas (21) returning to the CO separating ice chest (4), the permeable gas (22) rich in H2 returning to the pressure-changing, absorbing hydrogenizing unit (6). An INDEPENDENT CLAIM is an integral system for separating carbonyl composite feed gas comprising low temperature methanol purifying unit (1), pre-absorbing unit (3), CO separating ice chest (4), a pressure-changing, absorbing and hydrogenizing unit (6) and a feed gas cooler (10); in which the feed gas cooler (10), the low temperature methanol purifying unit (1), the pre-absorbing unit (3) and the CO separating ice chest (4) are connected to each sequentially; H2 feed gas outlet of CO separating ice chest (4) is connected with the inlet of the pressure-changing, absorbing and hydrogenizing unit (6); further comprising a film separating unit (8); the inlet of the film separating unit (8) is connected with the desorbing gas outlet of the pressure-changing, absorbing and hydrogenizing unit (6); the CO enrichment gas outlet of the film separating unit (8) is connected with the inlet of the CO separating ice chest (4); the permeable gas rich in H2 of the film separating unit (8) is connected with the inlet of the pressure-changing, absorbing and hydrogenizing unit (6).