TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: Separating carbonyl composite feed gas comprises adding precise filtering process after the washing with the low temperature methanol and before processing with the molecular sieve, filtering the methanol clamped in the feed gas after low temperature methanol washing. The pressure of the intermediate pressure flash vessel generated in the process of low temperature methanol washing is 0.8-2MPa, flash vessel (27) generated in the CO ice chest (4) mixes with the carbonyl composite feed gas after pressurizing with the intermediate pressure flash vessel. It comprises in low temperature methanol washing and molecular sieve absorbing and processing after the carbonyl composite feed gas heat-exchanging by the feed cooler (10); the tail gas (31) generated in the process of the low temperature methanol washing, the flash vessel (27) generated in the CO separating ice chest (4), the CO product gas (14) and the H2 feed gas (24) recovering by the feed cooler (10) and cooling and then entering the downstream process. The temperature of the feed gas (13) entering in the CO separating ice chest (4) is minus 38-minus 58 degrees C, the pressure of the CO product gas (14) is 0.3-1.5Mpa, and the pressure of the H2 feed gas (24) is 2.8-7.8Mpa. The CO separating ice chest (4) comprises a plate-type heat-exchanger (50), a washing tower (51), a reboiler (52) and a stripping tower (53); the feed gas (13) heat-exchanges by the plate-type heat-exchanger (50) after molecular sieve absorbing, and then enters the reboiler (52) to form the liquid-gas mixed feed (54), finally enters the washing tower (51) to separate to obtain the H2 feed gas (24); the CO enrichment gas (21) from the film separating unit (8) heat-exchanges by the plate-type heat-exchanger (50), enters the stripping tower (53) to separate to obtain the CO product gas (14); at the same time, taking the liquid material (55) from the stripping tower (53) and sending to the washing tower (51), further washing CO in the H2 feed gas (24); the CO material acquired from the bottom of the washing tower (51) returning to the stripping tower (53) to further separate. The H2 feed gas (24), CO product gas (14) and the flash vessel (27) are recovered and cooled by the plate-type heat-exchanger (50), and then enter the feed cooler (10) to recovering the cold material. The temperature of the CO enrichment gas (21) from the film separating unit (8) after heat-exchanging in the plate-type heat-exchanger (50) is minus 165 to minus 192 degrees C; the pressure for controlling the gas-liquid mixed feed (54) entering the washing tower (51) is 0.2-0.5MPa higher than that of the H2 product gas (24), and controlling the temperature minus 165-minus 192 degrees C. It comprises in controlling the pressure of the normal desorbing gas (19) entering the film separating unit (8) as 2-3MPa in the film separating unit (8); controlling the molar ratio of CO in CO enrichment gas (21) as 67-88 percent; the pressure for controlling the permeable gas (22) rich in H2 returning to the pressure-changing, absorbing and hydrogenizing unit (6) 0.2-0.5MPa higher than that of the H2 feed gas (24) acquired from the CO separating ice chest (4). Preferred System: In the integral system, the precise filter (2) is disposed between the low temperature methanol purifying unit (1) and the pre-absorbing unit (3). The flash vessel outlet of the CO separating ice chest (4) is connected with the inlet of the low temperature methanol purifying unit (1). The flash vessel outlet of the CO separating ice chest (4) is connected with the inlet of the low temperature methanol purifying unit (1) by the feed gas cooler (10); the tail gas outlet of the low temperature methanol purifying unit (1) is communicated with the outside by the feed gas cooler (10); H2 feed gas outlet of the CO separating ice chest (4) is connected with the inlet of the pressure-changing, absorbing and hydrogenizing unit (6) by the feed gas cooler (10); and the CO product gas outlet of the CO separating ice chest (4) is communicated with outside by the feed gas cooler (10). The CO separating ice chest (4) comprises the plate-type heat-exchanger (50); the washing tower (51); the reboiler (52) and the stripping tower (53); in which the inlet of the reboiler (52) is connected with the outlet of the pres-absorbing unit (3) by the plate-type heat-exchanger (50); the outlet of the reboiler (52) is connected with the inlet of the lower part of the washing tower (51), the bottom outlet of the washing tower (51) is connected with the upper inlet of the stripping tower (53); the top of the washing tower (51) is provided with the H2 feed gas outlet; the upper liquid material outlet of the stripping tower (53) is connected with the upper inlet of the washing tower (51); the other inlet of the stripping tower (53) is connected with the CO enrichment gas outlet of the film separating unit (8) by the plate-type heat-exchanger (50); the bottom of the stripping tower (53) is provided with the CO product gas outlet; the top of the stripping tower (53) is provided with the flash vessel outlet. The top H2 feed gas outlet of the washing tower (51) is connected with the inlet of the pressure-changing, absorbing and hydrogenizing unit (6) sequentially by the plate-type heat-exchanger (50) and the feed gas cooler (10); the bottom CO product gas outlet of the stripping tower (53) is connected with the outside by the plate-type heat-exchanger (50) and the feed gas cooler (10); the top flash vessel outlet of the stripping tower (53) is connected with the inlet of the low temperature methanol purifying unit (1) sequentially by the plate-type heat-exchanger (50) and the feed gas cooler (10).