Abstract: BHG －5 welding wire is a GMAW filler wire which is widely used in domestic market，and its deposited metal possesses excellent mechanical properties when welding with shielding gas of 80%Ar+20%CO2．The mechanical properties and microstructure of BHG －5’s deposited metal were test and analyzed in this paper，the relativity between microstructure and mechanical properties and toughening mechanism were discussed．