Due to increasing requirements of energy efficiency, environmental protection and consumption of resources industries pay more attention to these subjects. The aim of this research is to analyse a walking beam furnace of voestalpine Stahl GmbH Linz particularly with regard to thermotechnical aspects and highlight possible potentials for increasing its energy efficiency. The first part of this thesis shows the functionality and mode of operation of a walking beam furnace and summarises the measures required to maximise their efficiency. An energy balance, supplemented with other types of calculation, forms the basis of the energy evaluation of the furnace. Generally there are three ways to increase energy efficiency, oxygen concentration of the exhaust gas being the most important. Beside the calculations there are some experiments in the practical part of this thesis, which are used for finding the reason for the high oxygen concentrations. Based on experiments an excess of air is implausible. Due to further experiments a relationship between oxygen concentration and the amount of combustion air pressure was detected. The mode of the reheating furnace can only be maintained within a certain scope of air pressure, but with an optimization of the furnace system a reduction of the oxygen concentration is possible. A calculation of the inflow combustion air quantity led to a hyperstoichiometric combustion being detected, which causes a high oxygen concentration in the furnace. Due to this insight, an optimization of the burners is recommended. The thesis ends with a short financial view and the procedure of a possible future experiment is given.