The vacuum diffusion bonding was used to weld 93W to Ta using Ni as an interlayer. Universal testing machine was used to test the shear strength of the bonded joint. The microstructure of the bonded joints was investigated by XRD, SEM and EDS. The results show that the shear strength increases with the increasing of bonding temperature and holding time, and exhibits a maximum value of 244 MPa. The joint is composed of the Ni/Ta and Ni/93W interface. The phases of hcp-Ni3Ta，fcc-Ni3Ta，Ni2Ta and Ni4W are formed in the interfaces. The fracture of the joint takes place in the Ni/Ta interface rather than the Ni/93W interface. The reaction process of the welding joints can be divided into the following stages: effective physical contact, solid solution forming, intermetallic reaction layer forming, and intermetallic layer growing.