Abstract: By using the droplet size meter, the growth of fine particulates of typical coal ash components, including quartz, ferric oxide, calcium sulphate and mullite, was investigated in supersaturated water environment. The supersaturated water vapor environment was built through the contact of hot water with cold air. The results show that the fine particulates with good wettability grow easily; the smaller the initial particle, the fast it grows. The temperature of hot water has a great influence on the growth of particulates; higher temperature is favorable to form larger particulates. Overall, the diameter of particulates with different physical and chemical properties can be increased to 1 to 6.6 times larger at low supersaturation.