The invention discloses a method for coproducing methanol, natural gas for vehicles, and synthetic ammonia by using the hydrocarbon-rich industrial tail gas. The method is characterized in that the purified mixed raw material gas, namely a mixture of coke oven gas and carbide furnace gas, passes through a methanol synthesizer, a methanator, a pressure swing absorption and separation device and an ammonia synthesis reactor in sequence, to firstly separate the methanol; the separated methane can be used as the natural gas for vehicles; ammonia synthesis can be performed to the separated hydrogen gas and nitrogen; and pure hydrogen can be obtained by the excess hydrogen gas through pressure swing absorption after the ammonia synthesis is performed. Compared with prior art, the method has the advantages that the CH4 conversion is avoided, the CO transformation is avoided, and the air separation device is not provided. Therefore, the complexity of process is reduced, the useful component of the gas and the useful energy source can be comprehensively utilized in a cascade way, the raw material gas, the energy consumption, and the discharge amount of the carbon dioxide are all reduced, and the method develops a new way for the comprehensive utilization of the hydrocarbon-rich industrial tail gas of coke oven gas, carbide furnace gas, etc.