Reduction experiments were conducted with sintered Fe2O3–CaO–SiO2–Al2O3 tablets at (mass%CaO)/(mass%SiO2) (C/S) of 1.5, 2.0, and 2.5 at 1000, 1050, 1100, 1150, and 1200°C. From the reduction behaviors, we investigated the relationship between the reduction rate and C/S at the softening and melting zone temperatures of blast furnaces. The reduction rates at C/S = 2.0 and 2.5 increased with temperature in the range of 1000 to 1200°C. The reduction rate at C/S = 1.5 increased with temperature in the range of 1000 to 1150°C; however, at 1200°C, it decreased to the same value obtained at 1000°C. The microstructures of these samples, after sintering at 1270°C, pre-reduction at 900°C, and reduction at 1200°C, were analyzed through SEM-EDS. Fe2O3 particles, SFCA, slag, and pores among Fe2O3 particles existed in the samples after sintering. The matrix components in the pre-reduced sample were suggested to be calcium silicate slag containing FeOx and Al2O3 at C/S = 1.5, and to be ‘FeOx’ originated from SFCA at C/S = 2.0 and 2.5. The porosity of the open pores at C/S = 1.5 decreased to 16%. It was found that the reduction rate at 1200°C decreased due to this lower porosity. By contrast, the porosity of the open pores after reduction at C/S = 2.0 and 2.5 was much higher than that after pre-reduction. The reduction rates of these samples at 1200°C were found to not decrease as a result of maintaining a higher porosity.