The invention discloses a method for preparing methyl mercaptan through a reaction of methyl chloride and hydrogen sulfide. The method comprises the following steps: inflating quantitative methyl chloride and hydrogen sulfide gas into a reactor in which a catalyst is added, and performing a chemical reaction at a certain temperature and under a certain pressure, cooling after the completion of thereaction, and separating to obtain the methyl mercaptan. By the method, the gas-gas reaction is adopted, the operation is simple, a target product has high selectivity and high purity, no waste wateris produced in the process, the pollution is low and a byproduct is mainly hydrogen chloride which can be sold as a product, so that the method has a relatively great economic significance.