To meet the requirements of drying processes, this paper proposes a theoretical design method for a natural gas-fired hot blast furnace suitable for this scenario, while establishing a numerical model for it. It also focuses on analyzing the influence laws of three types of geometric parameters—air inlet angle, air inlet diameter, and combustion chamber length—on the internal flow field of the furnace and the outlet temperature. The simulation results show that increasing the air inlet angle of the cooling chamber can significantly optimize the temperature distribution; reducing the air inlet diameter can effectively increase the air inlet velocity and further improve the outlet temperature uniformity; while under the same heat output condition, the combustion chamber length has a negligible impact on the outlet temperature. However, when the air inlet velocity is relatively high, increasing the combustion chamber length can enhance the outlet temperature uniformity. The experimental verification results indicate that the experimental data are in high agreement with the numerical model. Through the integration of theoretical calculations and numerical simulations, this study has further improved and refined the design method of natural gas-fired hot blast furnaces specialized for drying processes.