Abstract: Based on the effects of carbon,titanium and copper on the microstructure and mechanical properties of weld metals,a high strength and toughness microalloyed welding wire contained copper for GSAW was developed.A series of test were done,including measurements of conventional mechanical properties,impact energy-temperature,drop-weight,dynamic tear and CTOD.The weld metal showed very good toughness at low temperature,and dominant microstructure of acicular ferrite.