Abstract: The reduction of the synthetic and practice blast furnace slags with carbon at high temperature was carried out. Over 2123 K and 2173 K the SiO₂ and MgO can all be reduced respectively, but at 2 273 K the Al₂O₃ will be reduced only 63%. In the increasing of MgO at constant basicity of the synthetic slag, SiC and SiO formed by reducing SiO₂ in the slag can be increased and decreased respectively at the relative high tempeyature and enough carbon. By increasing the temperature and well mixing the practice slag and carbon, the reduction of oxides in the slag and Al₂O₃ in the reduced slag will be increased, SiC and MgO in the reduced slag will be decreased. The MgO in the slag can all be reduced at relative high temperature.