Abstract: In order to eliminate the shortcomings of onerousness of calculation and of too many memory spaces needed in the practical calculation of establishing the heat transfer mathematical model of flame furnace by the zone method, "furnace section imaginary area" zone method has been developed in this paper. The predicated calculation of two oil-fired continuous reheating furnaces has been carried out using this method. The radiant direct exchange areas have been solved by applying Dunkle's concept of geometric mean beam length of travel. The solution of the non-linear zone energy coupled equations is obtained by Broyden method. The calculating results show that in comparison with the conventional zone method, "furnace section imaginary area" zone method has the ad-vantage of simplicity, more accuracy, rapid convengency and occupying less memory space.