Desulfurization wastewater has special water quality and high water pollution. Flue evaporation technology of desulfurization wastewater has engineering practical value for the treatment of desulfurization wastewater. Aiming at the application of flue evaporation technology of desulfurization wastewater in engineering practice, the heat and mass transfer model of atomized droplets in the tail flue was established, and the evaporation characteristics of a large number of desulfurization wastewater in the tail flue of a 300 MW boiler were calculated by numerical simulation. The safe distance between the nozzle and the flue wall was calculated under different nozzle flow rates to determine the layout area of the nozzle in the flue section.Combined with the total amount of desulfurization wastewater, the number and location of the nozzle were determined， and the effects of flue gas temperature, velocity and droplet size on the droplet evaporation time and distance were analyzed. The results show that the safe distance increases with the increase of the spray flow rate and the droplet size, the decrease of the flue gas temperature and velocity and the increase of droplet size, so that the safe area gradually decreases. Due to the action of gravity, the safe distance between the nozzle and the lower wall is the largest. When the total amount of desulfurization wastewater is fixed, with the increase of the number of nozzles and the decreases of the spray flow of a single nozzle, the evaporation time and distance of the atomized droplets shorten, so that more wastewater can be treated within a certain distance. When the total amount of desulfurization waste water increases, the more the number of nozzles is, the smaller the increase value of the flow of a single nozzle is, and the smaller the increase of evaporation distance is, making the maximum treatment capacity stronger. With the same number of nozzles, the increase of flue gas temperature, flue gas velocity and droplet size will reduce the evaporation time and shorten the evaporation distance. In practical application,the actual situation of the unit should be combined to choose the appropriate nozzle layout and design the waste water flue evaporation system reasonably.