The invention provides a process and device for desulfurization and decyanation via a catalyst method. The device comprises a three-stage desulfurization and regeneration tower section and a pre-cooling tower section, wherein the coal gas outlet of the pre-cooling tower section is connected with the coal gas inlet of the three-stage desulfurization and regeneration tower section, and the coal gasoutlet of the three-stage desulfurization and regeneration tower section is connected with a saturator in an ammonium sulfate procedure by a cyclone demister. Compared with the prior art, the invention has the following beneficial effects: 1) the process and device provided by the invention are used for filling a gap of a certain steel mill in the field of coal gas purification, supplying high-quality reducing gas to a steel rolling system for the production of high-quality boards and providing powerful guarantee for production of high-value-added boards; 2) the process of the invention is a novel process developed on the basis of wet desulfurization and decyanation in consideration of the actual characteristics of working conditions and has the characteristics of low investment, high desulfurization efficiency, small floor space, high automation degree and the like; and 3) the process of the invention can ensure that the content of H2S and HCH in purified coal gas is 20 mg/Nm<3> or below.