Abstract: The main defects of the fog fan system are that the droplets can not be evaporated completely and wet ground while the system is operating. On the basis of actual evaporation amount measuring of the fog fan system in the course of the cooling, the paper analysed the main parameters, such as the nozzles height, pumps pressure, the diameter droplets, how to affect the evaporation amount. The study gives some guidline for design parameters to increase the evaporation efficiency and solve other problems of the fog-fan systems.