In this paper, the gas phase, particle phase and mathematical model of heat and mass transfer of SO2 and HCl in acidic flue gas spray drying were established. The influence of the droplet operating parameters on the acid flue gas purification was simulated. The relationship between the droplet displacement in the tower and the inlet flue gas velocity was studied. The influence of atomization humidification and slurry concentration on flue gas purification efficiency was studied experimentally. The experimental results show: Join the humidifying water in spray drying process, the removal efficiency of SO2 and HCl increased, and the removal efficiency of SO2 increased obviously. But the removal efficiency of HCl was not significantly increased. With the increase of the concentration of lime slurry, the removal rate of SO2 and HCl all decreased slightly, and the decrease of the removal rate of SO2 was less than HCl. The simulation results show that: When the inlet smoke velocity is 5 m/s, the displacement range of the droplet is large. With the increase of droplet size, the temperature gradually increased with time. The size of 30 μm, 60 μm and 90 μm droplet reaches stability at 3S, 3S and 4S, respectively. With the increase of particle size, the purification efficiency is increasing. The removal efficiencies of HCl reached equilibrium at 1.5 s, 1.7 s and 2 s, respectively, The removal efficiencies of SO2 reached equilibrium at 25 s, 35 s and 4 s, respectively. It can be seen that HCl achieves maximum removal efficiency shorter than that of SO2. The removal efficiency of SO2 and HCl increases with the temperature of inlet flue gas increasing. Compared with SO2, the removal rate of HC1 reached stability in the shorter time.