The flue gas desulfurization technology of catalytic cracking unit including the crude oil selection, hydrodesulfurization technology, SOx transfer catalytic agent application and flue gas desulfurization technology was briefly introduced. The flue gas desulphurization technologies, such as limestone/lime-gypsum desulfurization technology, sodium desulfurization technology, ammonia desulfurization technology, EDV desulfurization technology were mainly introduced.It is pointed out that the flue gas desulphurization technology with high desulfurization efficiency is an inevitable choice in order to meet the sulfur content index of catalytic flue gas, and enterprises should select appropriate desulfurization process according to their own conditions.