Continuous preheat furnaces is one of the primary elements of a hot rolling process. Its job is to reach slab's temperature at certain amount and keep it smoothly distributed in the slab. Hence, it is important to analyze heat transfer inside the furnace and find the heat flux and temperature distribution of slab in different sections of furnace. In this study, some of the numerical method that exists for analysis of radiative heat transfer in enclosure is brought under investigation. Total absorption factor, which is introduced by Gebhart, is calculated by Monte Carlo method. Then total energy balance between all surface and gaseous elements is written using overall absorption factor and solved using a iterative method. Results repeated for different load emissivities and furnace heights and concluded that by increasing load emissivity and decreasing furnace height, operating efficiency increase.