The estimation of the total heat exchange factor plays an important role while obtaining the reference trajectories on steady-state furnace operation for the reheating furnace control system. For this purpose, this paper presents a new optimization method to estimate the total heat exchange factor by solving the inverse heat conduction problem (IHCP) in the reheating furnace. The proposed method is based on the Conjugate Gradient Method (CGM), the Levenberg-Marquardt Algorithm (LMA) and Gradient Projection method (GPM). In the proposed method, CGM is introduced for its fast convergence speed and the high accuracy, LMA is employed to assure the convergence of iteration sequence, and GPM is guaranteed to identify the active set at a solution in a finite number of iterations. The experiment results using the real plant data measured by thermocouples and the comparison between the proposed method and CGM are discussed. The results show the effectiveness on overcoming oscillation manner by the proposed approaches. (C) 2017 Elsevier Ltd. All rights reserved.