Abstract: The hydrodynamics of fine particles in pressurized air-spouted beds with internal diameter of 186 and 80mm, respectively, was studied using alumina and silicon gel particles of the size ranging from 0.26 to 1.7mm at the operating pressure up to 700kPa.A model for the minimum spouting velocity( U _ms )has been established through a series of experiments.There are three different cases in the relationship between the operating pressure and U ms . U _ms increases in a way for a Re _t<2 range, decreases in a way for a Re _t=2-500 range and decreases evidently for a Re _t>500 range with the increase of the operating pressure.The experimental results showed that the spouting stability could be significantly improved by increasing operating pressure.The maximum spouted bed height and spout diameter increase with the increase in bed pressure.It was also found that the fountain height in the bed almost keeps constant with the increase in the operating pressure.