The macroscopical properties and the changing of microscopical performances of artificial fog have been studied. In terms of the discussion of the forming theory of fog, the difference between experimental results and the theoretical calculation was compared. The results showed that the granularity and liquid water content of artificial fog droplet were a few less than that of the natural fog while the droplet concentration of artificial fog was higher than that of natural fog. Furthermore, the fog size distribution was different between them.