Abstract: To study the evaporation laws of desulfurization wastewater in power plant, numerical simulations were conducted on the evaporation of atomized droplets injected into the rear flue of a boiler, so as to analyze the effects of operation parameters on the total evaporation time of the droplets, and finally to obtain the relationship between the flue gas temperature and the optimum mass flow rate through nozzles by fitting method. Results show that the evaporation time would be the shortest when the gas velocity through rear flue is 10 m/s and the initial velocity of atomized droplets is 5 m/s. At the optimum mass flow rate determined previously, the atomized droplets could be evaporated completely before entering the electrostatic precipitator (ESP), when the flue gas temperature is higher than the acid dew point. The mass flow rate of nozzle injection is linearly proportional to the evaporation time, which is negatively correlated with the temperature of the flue gas before entering the ESP.