Abstract: Experiment research on plasma arc welding of dissimilar metals between T2 copper and Q235 steel was carried out with LHM-200 plasma arc machine.A defect-free joint with good weld appearance was obtained.Microstructure of welded joint were analyzed by optical microscopy, and the effect rules of process parameters on mechanical properties of joint were analyzed.The results indicated that microstructure of the center of weld bead was like cell population shape.The microstructure characteristics of weld bead close with Cu-based metal was different with that close to Fe-based metal.The optical welding parameters were 65 A of weld current, 0.4 cm/s of welding speed, 0.7 L/min of plasma flow, and the tensile strength of welded joint reached 176 MPa with these parameters, and the fracture happened at the HAZ of copper side.