The invention relates to a method for preparation of natural gas by sulfurtolerant methanation. Specifically, coke oven gas and coal gas are compressed, then a part of the gas is transformed, the transformed gas and untransformed gas compose crude feed gas meeting requirements; the crude feed gas is subjected to sulfurtolerant methanation, then gas is purified to remove harmful gas hydrogen sulfide, the removed hydrogen sulfide is subjected to desulphurizing recovery, after purification, the gas is separated, the reaction generated methane and impurity components are separated to prepare natural gas, the separated H2, CO, CO2 and the like are subjected to pressure swing adsorption separation as purge gas, the separated H2 and CO are returned to sulfurtolerant methanation for recycling, and the separated CO2 and liquid ammonia are subjected to urea synthesis. The method provided by the invention has the advantages of good economical efficiency, improvement of feed gas utilization rate, and simple process.