Abstract: A mathematical model of RH-MFB process was developed. The temperature of molten steel can be calculated by Delphi program. The results show that the temperature of molten steel declines drastically in the beginning of refining, and the speed of temperature drop is approximately 3 ℃·min^-1 in the first 10 min. Al addition, blowing oxygen, alloy addition and the initial temperature of the vacuum vessel wall have more effect on the temperature of molten steel. A comparison between the calculated and measured temperatures shows that the values with average errors in ±5℃ is by 80 % for predicting the temperature of molten steel at the end-point of RH-MFB process.