Abstract: Hydrogen-rich gas injection into the blast furnace （BF） is a key technological pathway for achieving low-carbon metallurgy. However, existing mathematical models often simplify the pulverized coal combustion rate as a constant value, neglecting the competitive combustion effect between the hydrogen-rich gas and pulverized coal during co-injection. This leads to deviations in the evaluation of smelting indices and carbon emissions. To accurately assess the impact of coke oven gas （COG） injection on the BF process, this study first determined the pulverized coal combustion rates under different injection volumes via high-temperature combustion simulation experiments. By coupling these experimental data with a hydrogen-rich blast furnace mathematical model, the effects of combustion rate variations on the coke ratio, coke replacement ratio, direct reduction degree, theoretical combustion temperature, and carbon emissions were systematically analyzed. The results indicate that as the COG injection volume increases from 0 to 60 m³/t, the pulverized coal combustion rate decreases from 72.0% to 64.2%. Constrained by the reduced heat release from coal combustion and the endothermic nature of the hydrogen reduction reaction, the coke replacement ratio shows an accelerated downward trend, dropping from 0.45 at 10 m³/t to 0.40 at 60 m³/t. Nevertheless, COG injection effectively improves smelting indices, reducing the direct reduction degree from 0.454 to 0.387 and the coke ratio from 377.5 kg/t to 353.5 kg/t. Regarding the thermal regime, large-scale COG injection causes the theoretical combustion temperature to decrease from 2 207.7 ℃ to 2 085.7 ℃, while the top gas temperature rises from 197.37 ℃ to 213.87 ℃. To maintain stable thermal equilibrium in the hearth and shaft, a coordinated operation window for the oxygen enrichment rate and injection volume was established. Under an injection volume of 60 m³/t, the oxygen enrichment rate must be adjusted to the range of 5.70%-13.19%. Quantitative evaluation of carbon emissions reveals that the indirect reduction effect of hydrogen-rich gas plays a dominant role in carbon reduction, while the impact of competitive combustion is minor. The carbon reduction attributed to the chemical reduction effect of COG is 31.2 kg/t, whereas the increase in carbon emissions caused by competitive combustion is only 0.5 kg/t.