Abstract: Based on the principle of thermal balance and materials balance in lime furnace,a calculation model used for on-line testing the resolution ratio of baked limestone in lime furnace is conducted by using of parameters that can be measured in spot.For a lime furnace in operating, the resolution ratio of baked limestone can be predicted on time by this model when mass input of limestone, coke ratio, air flux, concentration of carbon dioxide in outlet, temperature of flue in outlet and temperature of output lime are measured in-line. The calculation model has been testified with gained actual parameters and proved to be operable.After the model are programmed and joined into computer test & control system,that will provide strong support for operation optimizing and auto-test and control of lime furnaces.