Abstract: The performance and flaw of welded joint have always been important aspects of the welding material on this subject. A lot of research has described the performance and characteristics of welding joint materials, but the research about interface of dissimilar welding material and cracking problems is not sufficient. The project is focused on solving the problems of interface strength, microscopic mechanism and crack initiation of the T2 copper-45 steel bimaterial. The four-step measurement starts with using standard tensile and three-point bending experiment to calculate ultimate strength, yield strength and elastic modulus for fracture toughness. The macro/micro fracture morphology of tensile and three-point bending experiment are analyzed, characterizing the fracture surface morphology characteristics. It can be concluded that the fracture types of fracture are quasi-cleavage and intergranular brittle fracture mixed model. The deflection path of crack initiation is discussed and the crack is extended along the weld area and titled towards the T2-copper. Finally, based on experimental testing parameters and ABAQUS finite element analysis, crack propagation and deflecting direction of three point bending test result provide the basis for the improvement of the welded joint performance.