Abstract: Described in the article is the trial manufacture of the plasma arc-welded light-wall pipe in S32205 dual phase stainless steel. The influence on the weld seam structure and properties by heat treatment is investigated on the basis of the results of micro-metallographic test, tensile test under ambient temperature, spot corrosion test and explosion test, etc. It is concluded that both the temperature and time of heat treatment of S32205 dual phase stainless steel must be strictly controlled, otherwise excessive amount of ferrite will remain, and even σ or x brittle phase will be segregated, resulting in negative influence on the weld joint properties.