The present invention provides a method for synthesizing nitrogen-containing organic matters with high added values by virtue of a one-step method by activating methanol and ammonia gas molecules by means of a non-equilibrium plasma technology, namely a method for synthesizing methenamine and N,N-dimethylcyanamide. The method provided by the present invention has the advantages of low price of reaction raw materials and abundant sources, and belongs to one-step method synthesis. Moreover, the method provided by the invention has the advantages of being environmental-friendly, mild in condition, convenient to operate, simple in process, high in adaptability and the like, and can be used for synthesizing ethanol, formamide, ethanamide, aminoacetonitrile, N,N-dimethylcyanamide, glycol and 1H-1,2,4-triazole by further changing the condition. In addition, the method is suitable for synthesizing the nitrogen-containing compounds with high added values by any one or two of methanol, ethanol and propanol and the ammonia under the condition of non-equilibrium plasmas.