Abstract: The composite structure of stainless steel and aluminum alloy has the characteristics of low density and high thermal conductivity of aluminum alloy, as well as the high strength and corrosion resistance of steel. However, due to the large difference in the physical properties of the two kinds of materials, the joints of stainless steel and aluminum alloy are easy to produce brittle and hard intermetallic compounds by traditional welding method, which is resulting in poor weldability between the two kinds of materials. Therefore, the research of alloy dissimilar metal friction welding has important theoretical significance and practical application value. The welding temperature field is of great significance influence on the microstructure and the macroscopic morphology. Therefore, this paper uses commercial finite element analysis software to numerically analyze the transient temperature field of 304 stainless steel and 6061 aluminum alloy dissimilar metal butt friction stir welding. The influence of welding speed on the temperature field is analyzed. The results show that the results of numerical simulation are basically consistent with the results of infrared thermal imaging experiments, indicating that the heat source model has high calculation accuracy. By comparing the temperature distribution on both sides of steel and aluminum, it shows that the peak temperature of the steel side is higher than the peak temperature of the aluminum side during friction stir welding.