Hydrogen production via steam reforming of bio-oil combining heat recovery of blast furnace slag was investigated via thermodynamic analysis in this paper. The addition of Received blast furnace slag just had a slight enhancement for hydrogen production from the steam reforming process of bio-oil at low temperature, and had almost no thermodynamic effect either promotion or restraint) for the steam reforming reaction equilibrium at high temperature where higher H-2 yield were obtained, no matter how much blast furnace slag was added. However, different masses of blast furnace slag as heat carrier supply different added. However, different masses of blast furnace slag as heat carrier supply different amounts of heat, so the optimal blast furnace slag addition was performed via energy balance. If the sensible heats of the reformed gas and the slag after steam reforming re- actions were unrecycled, the required mass of blast furnace slag was over 30 times of bio-oil mass, while the required slag mass was just 11.5 times of bio-oil mass if the sensible heats after the steam reforming reactions were recycled. For the latter, about 0.144 Nm(3) H-2 per kg blast furnace slag was obtained at the reforming temperature of 700-750 degrees C and the steam/carbon mole ratio of 6. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.