TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: In drying and liquefying natural gas, according to refrigerant circulation process in the plate-fin heat exchanger, refrigerant from the compression system of the liquid-phase refrigerant enters into the heat exchange channel of the first group of the heat exchanger in the cold box. The absorption drying system adopts two towers or tower pressure swing adsorption drying technology, adopting molecular sieve adsorption dehydration, removing the water to the normal pressure dew point of less than or equal to 76 degrees C. The absorption drying system by the dehydrated natural gas enters into active carbon as a heavy hydrocarbon adsorbent purification system for removing heavy hydrocarbon, and then the cold case system liquefied subsequent. It adopts two towers or tower pressure swing adsorption drying technology, where each adsorption tower is provided with at least one molecular sieve for dehydration adsorbent bed layer and used for removing at least one active carbon absorbent bed layer hydrocarbon is any one of, preferably each of the absorption tower is provided with for dehydration is 2-16, preferably 3-8 molecular sieve adsorbent bed layer and any one of the used for 2-16 heavy hydrocarbon, preferably 3 to 8 of active carbon absorbent bed layer. Operating comprises processing the methane mixed gas in which absorption drying system is divided into two parts, one part is used as process gas stream into the drying process, and the other part is used as regeneration gas into the regeneration step. The absorption drying system is operated according to the following method: the acid treatment after the mixed gas of methane and carbon monoxide rich first through flow control valve is divided into two paths. Preferred Device: The top end of the gas-phase heavy hydrocarbon separator in turn through the sixth heat exchanger unit is further through the heat exchanger unit to the other heat exchange passage after the cold box. The adsorption drying system is divided into three paths through the second valve. Each of the first drying towers of each composite adsorbent bed layer independently filling is selected from 3A or 4A molecular sieve, active alumina, active carbon and water or a combination of two or more adsorbent silica gel.