The invention belongs to the technical field of environmental protection, and discloses a flue gas desulfurization catalyst and the application thereof to flue gas desulfurization in a decomposition furnace of a novel dry-process cement kiln. The flue gas desulfurization catalyst comprises the following components in percent by mass: 30-60% of manganese slag, 10-42% of nickel slag, 20-40% of copper slag, 10-30% of steel slag and 0.1-0.5% of cobalt oxide, altogether 100%. The flue gas desulfurization catalyst is uniformly mixed and ground and is then added at a raw material mill, a kiln hoist or a decomposition furnace coal injection pipe, and the SO2 concentration of flue gas can meet the standard when the addition amount is only 0.01-0.1% of the mass of a cement raw material. CaO desulfurization in the decomposition furnace is fully used for achieving the flue gas desulfurization; the flue gas desulfurization catalyst is easy to produce, easy and convenient to use and low in cost, isespecially suitable for the desulfurization of cement kiln flue gas with medium and low sulfur emission, and has an important practical significance on solving the problems of resource utilization andenvironment pollution of a high-sulfur raw material in the cement industry.