SO2 Emission of sintering flue gas accounts for more than 70% of total SO2 emission of steel industry. The purpose of this paper was to use steel slag for desulfurization of sintering flue gas. Based on traditional circulating fluidized beds (CFB) for flue gas desulfurization (FGD), a new dry digestion CFB-FGD process was developed. The new process eliminated the traditional digestion procedure, and the functions of the reactor include preliminary dust collection, digestion and desulfurization. An pilot CFB installation with maximum flow rate of 8000 Nm3/h for flue gas desulfurization was established. The desulfurization effects of calces, converter slag and blast furnace slag were investigated under the following experimental conditions: temperature of inlet flue gas, 150 °C; temperature of outlet flue gas, 75 °C. Relative humidity, 13%; flue gas flow rate, 6800 Nm3/h; Ca/S ratio, 1.2. The results showed that all of the desulfurization agents had desulfurization capability and the desulfurization efficiency of calces was the best, followed by converter slag and blast furnace slag. The removal efficiency of steel slag ranged from 75% to 82%. Considering solid waste utilization, the application of steel slag in desulfurization using dry CFB has a promising future.