30CrMnSiNi2A steel has become an important material for manufacturing aircraft landing gear and flaps due to its excellent mass-strength ratio. The welding speed of electron beam welding has a great influence on the microstructure and mechanical properties of 30CrMnSiNi2A steel in engineering applications. The microstructure of the joint transforms from the small equiaxed tempered sorbite and martensite mixed structure in the heat-affected zone to dendritic lath martensite grains in the weld area. The microhardness gradually increases from the base metal to the center of the weld. The microhardness of the weld area can reach up to 690HV0.2, which is about twice that of the base metal; the tensile strength is up to 842MPa, reaching 96.9% of the base metal strength. In addition, as the welding speed increases, the grain size decreases and the microhardness increases. However, the decrease in the number of HAGB and cementite is not good for the strength of the joint, so that the tensile strength of the joint decreases with the increase of the welding speed. The fracture mode of the lower joint is brittle fracture.