Due to its complex composition, low temperature, high concentration of SO₂ and large flow fluctuation, the flue gas of the vertical furnace pellet puts forward higher requirements for the flow field distribution of desulfurization process of the circulating fluidized bed. By analyzing the desulfurization mechanism of circulating fluidized bed and the factors affecting desulfurization efficiency, a Fluent numerical simulation method is used to research the influence of venturi arrangement, spoiler ring in the tower and dust collector deflector on the flow field of circulating fluidized bed, while an example of pellet flue gas reform in a steel plant is combined to verify the reliability of the simulation analysis. The simulation results show that, after symmetrically arranging the venturi tube at the flue gas inlet of the desulfurization tower, the velocity deviation of the gas flow is reduced to 5.70%. After adding a spoiler ring in the tower, the velocity mutation is increased to 9.80 m/s. After adding a deflector plate at the inlet of the bag filter, the speed deviation of each chamber is reduced to 7.53%, and all the above improvements meet the design requirements. After the project is put into production, the mass concentration of SO₂ and particulate matter in pellet flue gas is less than 20, 5 mg/Nm³, respectively, which is superior to the ultra-low emission standard of iron and steel industry and can run stably for a long time.