Abstract: The low-cycle fatigue properties of 26 mm thick 30CrMnSiNi2A ultra-high strength steel plate electron beam welded joint and base metal were studied. The results show that the low-cycle fatigue performance of the base metal is slightly higher than that of the joint, and the strain fatigue limits of the base metal and the joint are 0.50% and 0.48%, respectively. The fatigue fracture position of the welded joint is in the base metal. The fatigue crack sources are all on the surface of the samples,showing the characteristics of multi-source cracking, the fatigue crack propagation areas show typical fatigue lines. Lots of dimples are found in the final tensile fracture zone. The microstructure of the base metal, heat affected zone and weld metal of the joint is similar, which is tempering martenite, but the grain size of the weld metal is bigger.