NOVELTY - Preparation of liquefied natural gas involves degreasing coke oven gas, performing deamination reaction, performing heat-exchange reaction of processed coke oven gas, performing sulfur-tolerant methanation reaction and hydrogenation of organic sulfur in three stages, cooling, adding resultant product to low-temperature methanol wash system, removing sulfur, carbon dioxide, 2-4C hydrocarbon and impurities, adding to gas-liquid separation tank (H) and discharging gas at top of the tank and liquefied gas as bottom product.    USE - Preparation of liquefied natural gas (claimed).    ADVANTAGE - The method enables preparation of liquefied natural gas having high methane content of 97% or more and quality, by simple and economical process with reduced energy consumption.    DETAILED DESCRIPTION - Preparation of liquefied natural gas involves degreasing coke oven gas, performing deamination reaction, removing benzene and naphthalene, performing heat-exchange reaction of processed coke oven gas with outlet gas of sulfur-tolerant methanation reactor, adding heated coke oven gas material to sulfur-tolerant methanation reactor (A), performing primary stage sulfur-tolerant methanation reaction using molybdenum-based catalyst and hydrogenation of organic sulfur, transferring outlet gas to waste heat boiler (C) for heat recovery, adding processed material to sulfur-tolerant methanation reactor (B), performing secondary stage sulfur-tolerant methanation reaction using molybdenum-based catalyst and hydrogenation of organic sulfur, transferring outlet gas to waste heat boiler (D) for heat recovery, transferring portion of gas to recycle gas compressor buffer tank, discharging condensate water from buffer tank, transferring vapor to recycle gas compressor and mixing with fresh oven gas which is added to sulfur-tolerant methanation reactor (A), cooling remainder portion of gas, adding to gas-liquid separation tank (G), transferring vapor to sulfur-tolerant methanation reactor (E) through heat exchanger, transferring gas phase from sulfur-tolerant methanation reactor (B) to sulfur-tolerant methanation reactor (E), performing tertiary stage sulfur-tolerant methanation reaction using molybdenum-based catalyst and hydrogenation of organic sulfur, transferring reacted gas to waste heat boiler (F), cooling, transferring to gas-liquid separation tank (H), separating condensed water from bottom of tank (H), discharging separated gas at top of tank (H), transferring gas to pre-cooling heat exchanger, adding to low-temperature methanol wash system, removing sulfur, carbon dioxide, 2-4C hydrocarbon and impurities, cooling resultant gas, adding to gas-liquid separation tank (H) and discharging gas at top of the tank and liquefied gas as bottom product.