This paper briefly describes the general situation of the desulfurization project of a 4 000t/d cement clinker production line, compares the characteristics and application of wet and semi-dry desulfurization processes, and introduces in detail the selection principles of desulfurization schemes and the configuration of this desulfurization system. After the limestone-gypsum desulfurization system put into operation, the sulfur dioxide emission concentration at the outlet of the main chimney is reduced to 30mg/Nm³, which is superior to the latest emission standards of both national and Shandong Province. The desulfurizer is the recycled ash from the preheater, which can save about  530 000 yuan of cost per year. The by-product desulfurized gypsum can be directly used in cement production, which can create an economic benefit of 280 000 yuan per year.