Abstract: The effects of the adsorption of Al2O3 inclusion of different contents on the melting temperature, viscosity, surface tension and crystallinity of the mould flux were studied. The results showed that the melting temperature and viscosity increase but the surface tension decreases after the Al2O3 inclusions are adsorbed. When the basicity of mould flux is in the range from 0.85 to 1.17, the changes in its melting temperature and viscosity are small with the adsorbability kept well. When the basicity is in an appropriate range from 0.92 to 1.07, the surface tension changes little so as to benefit the adsorption of inclusions. With the increasing of Al2O3 inclusions, the quantity of cuspidite and grammite in mould flux decrease.