NOVELTY - Producing synthetic natural gas from coke oven gas using methane synthesis, comprises performing exothermic reaction on purified coke oven gas in first methane synthesis reactor, generating ultra high pressure steam through waste heat boiler, discharging gas and conveying into second methane synthesis reactor, mixing and generating ultra high pressure steam; filling low temperature methane synthesis catalyst into third methane synthesis reactor, conveying the gas, and raising gas temperature; and deep freezing the discharged gas to separate e.g. methane, and obtaining liquefied natural gas.    USE - The method is useful for producing synthetic natural gas from coke oven gas using methane synthesis (claimed).    ADVANTAGE - The method reduces equipment investment and operation and maintenance costs, increases production synthesis of natural gas and high quality by-product (ultrahigh pressure steam).    DETAILED DESCRIPTION - Producing synthetic natural gas from coke oven gas using methane synthesis, comprises (a) purifying coke oven gas; (b) conveying purified coke oven gas into a first methane synthesis reactor, performing exothermic reaction by raising gas temperature from 260-300 degrees C to 600-700 degrees C and generating ultra high pressure steam of 11 MPa through a waste heat boiler, discharging gas with high carbon content from the waste heat boiler and conveying it into a second methane synthesis reactor, mixing by raising gas temperature from 260-300 degrees C to 600-700 degrees C and generating ultra high pressure steam of 11 MPa through the waste heat boiler; (c) filling a low temperature methane synthesis catalyst into a third methane synthesis reactor, which is a low temperature reactor, conveying the gas, and raising gas temperature from 260-300 degrees C to 600-700 degrees C; and (d) discharging gas from the low temperature methane synthesis reactor, deep freezing the gas to separate methane and multi-carbon hydrocarbon liquid, and obtaining liquefied natural gas with hydrocarbon content of more than 94%.