Abstract: A new type of diffusion burner for steel rolling heating furnace was proposed based on fuel classification theory.To study its combustion characteristics, a full-size three-dimensional model was established using ANSYS Fluent software and numerical simulations were conducted. By adjusting the angle of the secondary gas nozzle and optimizing the structure of the prototype burner, the flame length was adapted to the design furnace length. By adjusting the operating power and excess air coefficient, the classification and combustion characteristics of the burner under different working conditions after structural adjustment were explored. The results show that the smaller the angle of the secondary gas nozzle of the burner, the longer the flame length, and it meets the design requirements at 17°. With the increase of the excess air coefficient,the temperature of each combustion zone decreases, the flame shortens, and NO_x emissions decrease. With the increase of the operating load, the temperature inside the furnace increases, the flame grows, and NO_x emissions increase. The air and gas classification ratio remains stable under various simulated operating conditions. The research results provide a certain reference basis for the optimization design and industrial application of burners.