Abstract: The tin bronze/steel diffusion bonding molecular dynamics model was established. The diffusion behavior of tin bronze/steel at different diffusion temperatures （1 073, 1 123, 1 148, 1172 K） after holding for 8 ns at the atomic scale was studied, the diffusion mechanism was analyzed, and the model was verified by experiments. The results show that the simulation and experimental results were highly consistent: under different diffusion temperatures, asymmetric diffusion phenomena occurred at the diffusion interface between tin bronze and steel, compared with the diffusion of copper atoms into iron, more iron atoms diffused into copper and the diffusion distance was longer. The diffusion activation energy of copper atoms at the interface was smaller than that of iron atoms, and the diffusion rate was larger, but the bonding between iron atoms was more difficult to break, and copper atoms were difficult to penetrate into the interior of the iron lattice. Copper was more prone to lattice defects, and iron atoms diffused slowly and deeply into the copper interior. Diffusion temperature was an important parameter affecting the atomic diffusion behavior. With the increase of diffusion temperature, the thickness of the diffusion layer and the mean square displacement of iron and copper atoms both increased. The diffusion bonding joint prepared at 1103 K for 8 ns had a concave-convex interlocking morphology at the diffusion interface, with a few copper atoms diffusing into the steel matrix to form Fe-Cu solid solution. The diffusion layer was the thickest （5.0 μm）, and the tensile strength was the largest （260 MPa）.