Rotary spray drying technology, as a zero-discharge treatment technology for desulfurization wastewater, has the advantages of good adaptability to wastewater, low energy consumption, low investment, and broad application prospects. A 600 MW thermal power plant unit desulfurization wastewater spray drying tower was used as the research object, an atomization evaporation model was established, and the numerical simulation study on the influence of the deflector angle in the spray drying tower on the atomization and evaporation performance of desulfurization wastewater was carried out. The results show that the gas distributor in the drying tower divides the flue gas into two flue gas flows through the inner and outer channels. The flue gas in the inner channel first contacts with the droplets after atomization of the evaporative desulfurization wastewater, which directly affects the evaporation of the desulfurization wastewater. The flue gas in the outer flow channel can inhibit the vortex effect generated by the flue gas in the inner flow channel, and prevent the spray of atomized droplets on the wall surface of the drying tower from causing corrosion. A low temperature area is formed below the atomizer, where the relative velocity and temperature difference between the flue gas and the droplets are relatively large, which is the main area for atomization droplet evaporation. The influence of the deflection angle of the inner deflector in the inner flow channel on the atomization and evaporation performance of waste water is more obvious than that of the outer deflector. The smaller the angle of the inner guide plate in the inner flow channel is, the larger the angle of the inner guide plate in the outer flow channel is, the more flue gas that enters the inner flow channel is, the shorter the evaporation time and evaporation distance of desulfurization wastewater is, and the more significant the improvement of its evaporation performance is. Comprehensive consideration, in actual operation, it is recommended to set the angle of the deflectors of the inner flow channel to 0°, and the angle of the deflectors of the outer flow channel to be set to 45°.