The behavior of Al2O3 in titanium slag was discussed by combining the production practice of electric-furnace with the theoretical basis of titanium slag smelting. It is concluded that the relative high Al2O3 content in titaniferous iron ore leads to increasing of the viscosity and the melting-point of high titanium slag, irregularity in furnace operation and technical-and-economic indexes depression. Besides, the relative high Al2O3 content in titaniferous iron ore also has negative influence on the enriching of TiO2 and the operation of chloridizing process.