Abstract: A mathematical model of gas flow, combustion and heat transfer in the pusher-type slab reheating furnace was developed with the commercial CFD software Fluent to compute the flow and temperature fields and the concentration distribution of the reactants/products from combustion. Numerical results showed that the average temperature of furnace will come up to 1300°C when the temperatures of preheated air and coal gas are 350°C and 50°C, respectively. Thus, it is available to meet the requirement for slab's reheated temperature. The recirculation flow due to the complex geometry of furnace, is found obviously, and the combustion air preheating can raise the gas temperature in furnace efficiently so as to improve the furnace's thermal efficiency especially during full combustion. Such results may be taken as important reference for the optimal design and operation of reheating furnaces.