Abstract: Austenitic 321 stainless steel is always used as the main pipeline material for nuclear reactor coolant. The lead-bismuth eutectic (LBE) alloy is a primary candidate coolant for the lead-cooled fast reactor for the fourth generation nuclear power system (Gen Ⅳ). The compatibility of 321 stainless steel and LBE alloy at 550 ℃ for 200, 400 and 600 h was studied. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) were carried out on the surface and cross section of corrosive samples with different corrosive time. A compound containing O, Ti and Pb elements (Ti₂O and Pb₂O₃) is developed firstly on the surface of 321 stainless steel samples and peeled off with the increase of corrosive time successively. At the junction of 321 stainless steel matrix and LBE alloy, diffusion layer is thickened with time. In the process of corrosion, dissolution corrosion of 321 stainless steel occurs in the LBE alloy. Fe and Cr elements dissolve continuously in LBE alloy, meanwhile, Pb and Bi-elements infiltrate into the base metal.