Abstract: The molten iron is solidified out into white iron by using whiting elements. It changed the cooling curve of molten iron, and lost some important special points in cooling curve of thermal analysis. When the molten iron solidifys grey iron, the five special points of cooling curve can be used to forecast composition C and Si exactly. The linearity of special points is different. The other compositions and molten number affect accuracy of forecasting. This paper proposes the whitening compensation equivalent.