Abstract: Hot isostatic pressing (HIP) was used to bond the bar 316L stainless steel/T2 copper, and the microstructure and mechanical properties of the bonding interface were analyzed. The results show that the dissimilar metal joints are well bonded under the bonding mechanism of plastic deformation and diffusion reaction, and the elements on both sides of the matrix obviously have mutual diffusion. Finally, the diffusion layer with a thickness of 3.9 μm is formed. The diffusion layer is divided into the diffusion-affected zone (DAZ) on both sides and the reaction layer (RL) in the middle. Dendritic γ-Fe phase, strip α (Cu, Ni) phase, and irregular massive Cr-rich phase precipitate on the diffusion layer and adjacent side of T2 copper. Hardness test results show that the hardness of the joint is higher than that of the weak T2 base metal. The average hardness of the joint is 94 HV0.1, and there is no hardness mutation, which that indicates no brittle intermetallic compound was formed. A ductile fracture happened at the T2 base metal during the tensile test, with the maximum tensile strength of 165 MPa. Joints and their adjacent diffuse distribution of the precipitated phase formed a second phase strengthening mechanism, which has hindered the dislocation movement, and thus enabled the joint with better hardness and bonding strength.