In this paper, the flow field in the desulphurization tower is studied deeply based on two-fluid model, particle dynamics theory and FLUENT. A numerical simulation analysis of fluid within the desulphurization tower is done and the desulphurization tower is the major equipment in the system. The simulation design and calculations show that the two-fluid model is reasonable to analyze the flow field. The simulation results show that smoke can form good reaction environment within the desulphurization tower. It is meaningful for the further optimization of designing desulphurization tower structure in the circulating fluidized bed system.