Abstract: To solve the scheduling problem of walking beam reheating furnaces with the energy consumption and productivity of hot rolling mills taken into account, a mathematical model was developed for the mixed charging of cold and hot slabs. The objectives were to minimize the practical heating time, waiting time for heated slabs during hot rolling and the number of the mixed chargings. An ant colony optimization (ACO) algorithm was therefore designed to solve the model, which was embedded in the local search process based on neighbourhood search, thus improving the convergence rate. Results of the simulation in according to actual production data of an iron/steel plant showed the effectiveness of both the model and algorithm proposed.