Abstract: LF refining process plays an important role in the temperature adjustment of molten steel, and precisely predicting the LF end-point temperature of molten steel is of great importance to actual production. Generally speaking, the prediction models of LF end-point temperature include the mechanism model and the black box model. The mechanism model can reflect the influence of each factor on the end-point temperature of molten steel, but it is dimcult to obtain the expected prediction accuracy due to the limited comprehension of heat transfer in LF refining process. The black box model can usually achieve high prediction accuracy, whereas it does not reveal the effect of each factor. Moreover, the black box model has limited applications when process conditions are changed. Taking LF refining process in Fangda special steel plants as an object of study, this paper establishes a grey box model for predicting the LF end-point temperature of molten steel based on the mechanism model and the black box model. The grey box prediction model can not only indicate the impact of each factor, but also provide the precise prediction of LF end-point temperature. Verification results show that the hit rate of the grey box model is greater than 95% while the predictive error is within ±5℃.