T2/Q345 steel-copper dissimilar metal welded joint is fabricated by argon tungsten arc welding with nickel-based welding material. X-ray diffractometer,metallographic microscopy,scanning electron microscopy,microhardness tester and universal materials tester are used to analyze the microstructure and properties of the welded joints. Weld metal and base metals on the both side in welded jonit have excellent physical and chemical compatibility. Weld metal consists of face-centered cubic γ phase with the apperance of columnar dendrite and equiaxial dendrite. Due to the heat source concentration of argon arc welding and high heat conductivity of the copper alloy,the range of the coarse grained region on both sides of the heat affected zone is very limited. Chemical composition analysis result shows that diffusion of Ni and Cr occurs in the T2 heat affected zone. Tensile testing result shows that the welded jonit fractures in the position of the copper alloy where the microhardness is minimum and the welded joint shows good mechanical properties.