Rotary spray drying technology with bypass flue is widely adopted to realize the zero-discharge of desulfurizationwastewater in coal-fired power stations. Significantly, the deflector structure of the dryingtower is an essential factor affecting the evaporation performance of desulfurization wastewater. Thispaper is aimed to study the effect of the angle and number of the deflectors on the evaporation performancein a drying tower of a 600 MW coal-fired station. Results show that the gas distributor dividesthe flue gas into internal and external parts, and the flue gas in the internal channel is the main factoraffecting the evaporation performance. The deflector angles (especially for the internal deflector) havea remarkable impact on the evaporation behaviors, while the deflector numbers just have a minor effecton that. When the deflector number is 24 and the angles of internal and external deflectors are set at 0and 45, respectively, a better evaporation performance is obtained with the weighted average time ofapproximately 0.17 s and the complete evaporation distance of approximately 3.93 m. These optimal settingsare adopted in the actual operation, and the industrial measured results show good performance isobtained.