Abstract: Field flue gas composition and heat balance tests were carried out on a 25t regenerative aluminum smelting furnace, and the material balance and heat balance calculations were carried out to obtain the mass flow distribution, heat flow distribution and ton of aluminum natural gas consumption in a single smelting cycle of the aluminum smelting furnace. The NOx emission characteristics were obtained by analyzing the changes of flue gas nitrogen oxide (NOx) concentration at different heating stages. The results showed that: The thermal efficiency of the furnace is 62.48%, and the consumption of natural gas per ton of aluminum is 72.1 Nm3/t. The main heat loss of the system is the heat loss of furnace body and pipeline and the heat dissipation loss, accounting for 14.24% and 11.98% of the total output heat respectively. The proportion of physical heat from ash and slag is small, but the burning loss and impurities will reduce the output quality of liquid aluminum. The energy consumption of aluminum smelting furnace can be reduced by shortening the melting time, reducing the amount of cooling air in non-ignition time and reducing the number of furnace door opening. The NOx emission concentration of the smelting furnace was higher than 600 mg/m3 for a long time, and the peak emission was 1 197.0 mg/m3. The NOx emission concentration can be reduced by optimizing burner structure parameters, optimizing operation parameters and applying high temperature air combustion technology.