Abstract: The reasonable billet space in walking beam furnace is of great significance to improve the productivity of the furnace. The related expressions of billet side heat flux were derived by using a radiation network, and the effect of billet space on heat-up time and furnace productivity were analyzed. What's more, the optimum space between billets was gotten using the extremum of relative productivity computed expression, which had been derived. Compared with the references, this study gets rid of the assume that the billet surface is bold and the expressions worked out are more general used, which has the important reference value to optimize the arrangement of billet and non-ferrous metal billet in the walking beam furnace.