The invention discloses a gas liquefaction system to conduct gas liquefaction by conveniently providing cold energy. The gas liquefaction system comprises a gas transportation passageway, a gas drive device, and at least two gas liquefaction devices which are arranged according to the level. The gas drive device is used for driving gas to enter the gas transportation passageway from the gas inlet end. The gas liquefaction devices are used for conducting liquefaction on gas entering the gas transportation passageway according to the level sequence. The gas liquefaction system further comprises a gasification device and a cold energy pipeline, wherein the gasification device is used for exchanging heat with liquid gas released by liquid and gas storage tanks of the gas liquefaction devices which are at the high levels or the same level and have obtained liquid gas when cold energy is required for the gas liquefaction reactions in any gas liquefaction device, and therefore gasification reactions can happen to the released liquid gas; the cold energy pipeline is used for transporting cold energy generated through the gasification reactions to any gas liquefaction device so that the cold energy obtained by any gas liquefaction device can exchange heat with hot energy generated when gas is compressed. In addition, the invention further discloses a gas liquefaction method.