NOVELTY - Producing methane comprises purifying coke oven gas, carrying out desulfurizing under a zinc oxide desulfurization groove, feeding the coke oven gas into a gas compressor, passing the raw material gas and pre-mixed steam into a multi-stage adiabatic fixed-bed reactor including methanation catalyst, where the hydrogen, carbon monoxide and carbon dioxide in the raw material gas undergo methanation reaction to generate a product gas methane and water, passing the product gas via methanation reactor outlet and separating to obtain synthetic natural gas (SNG) and compressed natural gas (CNG).    USE - The method is useful for producing methane (claimed).    ADVANTAGE - The method is simple and consumes less energy; does not adopts circulation process and reduces methane purification cost; and produces hydrogen gas as a by-product which can be used for manufacturing hydrogen peroxide or purification of coal tar, and can also be used for being converted into methane by adding carbon during methanation.    DETAILED DESCRIPTION - Producing methane comprises purifying coke oven gas, where the hydrogen sulfide content in the coke oven gas is less than 20 mg/m3, carrying out desulfurizing under a zinc oxide desulfurization groove to reduce the hydrogen sulfide content to less than 0.1 ppm, feeding the coke oven gas into a gas compressor for pressurization, passing the raw material gas and pre-mixed steam into a multi-stage adiabatic fixed-bed reactor including methanation catalyst, where the hydrogen, carbon monoxide and carbon dioxide in the raw material gas gradually undergo methanation reaction to generate a product gas methane and water, recycling excess hydrogen, where the product is recovered in two ways comprising: passing the product gas via methanation reactor outlet by at least two stages of heat exchange/cooling to reduce the temperature to 30-50 degrees C and removing the contained water, carrying out gas separation to obtain SNG and compressed natural gas CNG, where hydrogen after purification can be used as industrial hydrogen for anthraquinone hydrogenation of hydrogen peroxide or other hydrogenation process; and passing the complete coke oven gas with carbon dioxide having methane concentration of greater than or equal to 85% through the methanation reactor outlet, where the ratio of hydrogen to the sum of 3 carbon monoxide and 4 carbon dioxide is 1-1.1, gradually cooling, dehydrating and separating to obtain CNG and SNG.