Abstract: Elaborated in the article are the influences on the corrosion resistance of the low alloy steel by such factors as different alloy elements, weld microstructure type and grain size.Accordingly, the welding consumable, welding bevel and welding energetic parameters for the 50W weather-resistant steel are determined.Analyzed are the main aspects of the 50W steel, including welded joint microstructure, mechanical properties and corrosion resistance, etc.It is regarded via the analysis that when the weld metal of the 50W weather-resistant steel has a fine acicular ferrite structure, the welded joint demonstrates the best corrosion resistance.Accordingly, properly controlling cooling rate and welding heat input will make the weld have sufficient acicular ferrite structure, and thus get the 50W weather-resistant steel welded joint meeting relevant requirement for corrosion resistance.