Abstract: Air cooling fan is a new fogging system without pump and nozzle. To assess the distribution characteristics of droplets and provide the design and application parameters, the experiments were conducted under different water supply quantity and different vanes by using a Laser droplet testing instrument. The analysis showed that the droplet diameter distribution was normal in mass weight. The diameter of more than 90% of fogging particles was under 50 μm. The average diameter of fog droplets from cooling fan with four vanes was 10 μm smaller than that from cooling fan with two vanes, the difference of fogging efficiency of cooling fan with four vanes was 25%～47% higher than that of cooling fan with two vanes.