Spray drying process of cyclone spray drying tower was simulated numerically with software packages Fluent and Gambit, based on the pressure-swirl atomizer model. Rules of quality changes and residence time of particles in the drying tower were presented during drying process. The inlet air temperature, wind speed, material feed temperature and gravity, and other factors on evaporation efficiency were analyzed. The analysis result provides a reference for improving of optimal design and evaporative efficiency of cyclone spray drying tower.