Abstract: By analyzing the influence of the microstructure for weld deposited metal of high strength low-alloy steel on mechanical properties,the compound microstructure deposit with mainly the acicular ferrite(AF) and a small quantity of the granular bainite(GB) was applied to the welding wire for X80 pipeline steel.Based on the driving force concept of microstructure transformation,and combined with the acicular ferrite nucleated mechanism at nonmetallic inclusions and microalloy toughness theory,the Mn-Ni-Mo-Ti-B alloy was selected to study the welding wire of X80 pipeline steel.The results of experiments show that the weld deposited metal will fulfil the demands of strength and toughness and low-temperature toughness by choosing and controlling alloy elements rationally,and the developed 1#welding wire can be used for X80 pipeline steel.