CO2 emissions in steel works accounts for about 15% of those in Japan (2011), and most of those are from blast furnace iron-making process. To reduce CO2 emissions, utilization of woody biomass in blast furnace process is considered. Woody biomass has the characteristic of carbon neutral, as well as high reactivity. CO2 emissions can be reduced by the use of woody biomass as coke substitution because of its characteristic of carbon neutral. High reactivity of reducing agent is expected to decline thermal reserve zone temperature, which causes improvement of reaction efficiency in the blast furnace and lowering of reducing agent rate. To assess the adequacy of woody biomass as reducing agent, we evaluated the characterization of woody biomass with the coke reaction simulator (CRS). To verify the effect of the use of woody biomass on thermal reserve zone temperature, we executed experiments to evaluate the effect of woody biomass coexisting in the ore layer on reduction behavior of iron oxide with the adiabatic blast furnace inner reaction simulator (BIS). With heat and mass balance analysis, we evaluated the effect of declining thermal reserve zone temperature on lowering of reducing agent rate and the effect of utilization of woody biomass as coke substitution on reducing CO2 emissions in blast furnace process.