In order to improve the air supply uniformity of the blast furnace air supply system, a 3200m³ blast furnace air supply system of a factory is taken as the research object, the influence of the total air supply volume and tuyere diameter on the air supply uniformity of the system is analyzed by a numerical simulation method, and a specific improvement plan is given. The results show that the blast momentum of tuyere No.28 and No.12 is significantly smaller than that of other tuyeres under the condition of initial tuyere size, the maximum difference of blast momentum is 11.91 kJ/s, and the overall uniformity index is 2.31, indicating that the air supply uniformity of the system is not good. After adjusting the diameter of tuyere No.28 and No.12 to 130 mm, the overall uniformity index is reduced to 0.87. On this basis, increasing the diameter of all tuyeres and decreasing the total air volume can slightly improve the uniformity of air supply of the system, but the average blast momentum is decreased greatly. After adjusting the diameter of tuyere No.28 to 127 mm, No.12 to 130 mm, and No.26 and No.30 to 132 mm, the air supply uniformity of the system is significantly improved; the maximum difference of blast momentum is reduced to 2.27 kJ/s, and the overall uniformity index is reduced to 0.45.