Abstract: QCr0.8 TC4 electron beam welding process and the structure of joints were studied.The melting quantity of Cu alloy was lower due to its high thermal conductivity;moreover, there were lots of brittle intermetallic compounds in the weld, so the tensile strength of the joint was low.The non-centered electron beam welding was used to improve the tensile strength of Cu Ti joints.It was indicated that the tensile strength was increasing as the lateral deviation quantity increasing, and the maximum value, 270.5 MPa was obtained when the lateral deviation quantity was 0.8 mm.The fracture occurred near TC4 side, and it was quasi-cleavage crack.The weld was consisted of fusion zone and reaction layer near TC4 side. The fusion zone was mainly consisted of Cu-based solid solution with lower hardness than TC4.In the reaction layer, the component transition was obvious, and there were lots of intermetallic compounds. The thickness of the reaction layer was changed as the process parameter being varied, which influenced the mechanical properties of the joint.