Abstract: As a tool steel with high hardness, high wear resistance and high heat resistance, high speed steel often needs to be combined with dissimilar steel when applied to cutting tools, dies and special structural parts. However, the research on the welding process of high speed steel is still immature and the cracks and carbide defects in the welding are the main restrict factors of the application of high speed steel. In this paper, the electron beam welding of W6Mo5Cr4V2 high speed steel and 16Mn steel preplaced Ni intermediate layer effectively restrained the cracking of the heat affected zone of high speed steel side. The results showed that the joint was asymmetrical "funnel shape". The microstructure of the weld zone was mainly composed of nickel based solid solution and a small amount of M2C carbide. The plastic deformation ability of the weld was increased and the hardness of the weld reduced, which was 185 HV. The tensile strength with no defect joint was 378 MPa, which was 75% of the tensile strength of the 16Mn side. The tensile fracture occureed at the heat affected zone at 0.8 mm of the fusion line at the W6 side, and the fracture form was a quasi cleavage fracture with a certain plastic deformation.