Due to the massive amount of CO2 emission, it is required to reduce CO2 emission from blast furnaces. High reducibility of iron oxide on the initial melt formation stage is necessary to reduce CO2 emission. In order to estimate the effect of melt on reduction behavior and rate of sintered iron oxide pellet, heating-up reduction from 1000℃ to 1200℃ and isothermal reduction at 1200℃ were carried out. Samples were composed of Fe2O3, CaO, SiO2 and Al2O3. Three kinds of samples of different (mass%CaO)/(mass%SiO2) (C/S) were prepared in order to observe the effect of composition on the reduction rate. Reduction rate of samples were lowered over the initial melt formation temperature calculated by FactSage. Effect of melt formation on microstructure inside sample was observed by SEM and porosities were estimated by image analysis technique. Amount of melt increased and reduction rate decreased with increasing C/S. Pore occlusion ratio which was defined here increased with decreasing C/S and overall reduction rate decreased linearly with increasing pore occlusion ratio.