A mathematical model of a continuous reheating furnace has been developed to identify the design and operating parameters that significantly affect furnace performance. In this study, the furnace is modeled 3 dimensionally and theMonte Carlomethod is used to find the overall absorption factor. The overall absorption factor is then used to calculate the energy balance for furnace walls, the gas, and the moving slab. For this purpose, 1-D heat conduction in walls and 2-D heat transfer in the slab are assumed. Results include temperature distribution of gas, walls, and slab. The effects of emissivity of slab and furnace height on the efficiency of furnace are also analyzed. It is concluded that operating efficiency increases by increasing load emissivity and by decreasing furnace height.