Abstract: The raw material of 900 MPa high strength solid welding wire is low alloy steel wire bar, the drawing process can't continue due to the work-hardening and reduced plasticity. The wire bar after rough drawing was heat treated by different annealing processes, and the effect of annealing process on the microstructure and mechanical property of the wire bar was studied. The results show that when the annealing temperature is too high, the overcooling austenite transforms to hardening phase bainite during subsequent cooling of the wire bar, the tensile strength and the hardness are high, while the plasticity is low.When the wire bar is heated at 690℃for 6 h, cooled with furnace down to 300℃and then cooled in air, the microstructure is fine ferrite and globular pearlite. The microstructure has low tensile strength, hardness and good plasticity, which is favourable for subsequent drawing production.