The invention relates to a methanation method for synthesizing substitute natural gas by using industrial hydrocarbon exhaust gas. The methanation method comprises the following steps of: carrying out third-order or fourth-order methanation reaction on the feed gas of the industrial hydrocarbon exhaust gas; thermally recycling; and cooling and separating to produce a qualified synthetic natural gas product. CO and CO2 in the industrial hydrocarbon exhaust gas are completely converted into methane to achieve the purpose of zero emission of CO2. According to the methanation method, the gas passes through a multistage methane reactor once, CO conversion and CO2 separation are not needed, meanwhile, a segmented cycle and a compressor are not needed for the process gas, thus the investment cost and the operation cost can be greatly reduced; the process flow is simple, reliable and efficient; the operation is convenient and stable, the temperature is easy to control; the energy consumption is low; and the economic benefit is obvious. The synthetic natural gas produced by using the industrial hydrocarbon exhaust gas meets the international standards, and can be directly used for producing compressed natural gas and liquefied natural gas.