Abstract: 16 mm thick 2205 duplex stainless steel was welded with multipass at different welding parameters. The results showed that the welded joint of 2205 duplex stainless steel consists of austenite and ferrite, and multi pass welding results in more γ2. The content of ferrite in weld metal and heat affected zone were inversely proportional to the heat input. The impact test of the welded joints at －40 ℃ was carried out, the fracture appearances of low and high impact fracture toughness of welded joint were quasi cleavage fracture and ductile fracture, respectively. The toughness of welded joints was inversely proportional to the ferrite content.