Abstract: The foaming performance of LF refining slag with high basicity was investigated systematically and analyzed theoretically under lab conditions, with the molybdenum wire used to measure the height of foamed slag and the height taken as performance index. The results showed that the relative height of foamed refining slag increases with increasing slag viscosity and decreasing slag surface tension and slag density. In addition, when keeping the slag composition constant the relative height of foamed slag tends to increase first then decrease with increasing temperature and gas blowing flowrate. It was found that the proper composition of refining slag is w (CaO)/w (SiO2) 5-8, w (Al2O3) 27%, w (CaF2) 3%-6%, w (MgO) 8% and w (FeO) within 0.5% respectively.