To design and control furnace roller better, heat loss law of water-cooled furnace roller which surface coat is composed of heat-resistant alloy or asbestos fibers before and after improvement was studied by mathematical models. After analyzing the problems of traditional roller hearth furnace, the improvement reason and key point were pointed out. Heat transfer models for cooling process of two kinds of rollers were established and solved with iteration planning algorithm based on Newton search. Then, the relation between water flow velocity (uw), inlet water temperature (tw-in) and roller cross section temperatures, outlet water temperature (tw-out), water temperature rise (Δtw), cooling water heat absorption (Qw) was studied. The conclusions and recommendations are mainly as follows: 1) Roller cross section temperatures, tw-out, Δtw decrease with the increase of uw. The water critical velocity (uwcv) of two kinds of furnace rolls is 0.07 m／s and 0.09 m／s respectively, and when uw is larger than uwcv, turbulent flow occurs. Considering less water scale and water treatment system cost, tw-out should be under 45 ℃ and Δtw should be less than 10 ℃. So suitable uw should be 0.4～0.8 m／s and 0.2～0.6 m／s, when cooling water is entire turbulent flow, cooling efficiency is high, and Δtw is small, above which energy consumption increase greatly and uselessly, but Qw almost remains unchanged. 2) Qw of asbestos fibers roller is small and 78％ of heat-resistant alloy roller when cooling water is entire turbulent flow. Application result indicates that consumption of per ton steel is greatly reduced after the improvement and optimization control of furnace rollers, of which the reason is that production is greatly increased due to not grinding rollers, except for optimal control, fiber furnace roller heat loss is small.