Two-stage desulfurzations system including furnace desulfurization and flue gas desulfurization at circulating fluidized bed boils was proposed in order to improve the desulfurization efficiency of CFB boiler. Relying on the actual projects, the factors that affected the desulfuriztion efficiency were analyzed； the optical flue gas delsufurization configuration and the best match relationship between furnace delsufurization and flue gas delsufurization were suggested for the two-stage delsufurization system of CFB boiler. According to the specific engineering conditions, the reasonable configuration of two-stage desulfurization system was carried out. The results indicate that the CFB boiler can not only fully meet the current national environmental standards, but also improve the whole desulfurization operation efficiency.