To　study　the　tensile　stress-strain　relation　and　the　failure　mechanism　of　two　stainless　steel　types　(duplex　grade　S22053　and　austenitic　grade　S30408　stainless　steel　made　in　China)　and　the　corresponding　weld　metals,　tensile　tests　were　conducted　on　four　groups　of　test　specimens　including　three　duplicate　specimens　in　each.　The　fracture　micro-mechanism　was　analyzed　by　using　the　scanning　electron　microscopy　(SEM)　on　the　fracture　surfaces　of　the　specimens.　Based　on　the　experimental　stress-strain　curves,　the　parameters　of　the　material　constitutive　models　were　obtained　by　curve-fitting　using　the　modified　Ramberg-Osgood　equations.　Comparisons　of　the　tensile　stress-strain　relation　were　made　between　the　base　metal　and　weld　metal.　The　results　indicated　that　both　base　metal　and　weld　metal　fractured　in　a　ductile　manner,　and　their　stress-strain　relations　exhibited　significant　nonlinearity.　Compared　with　the　base　metal,　the　weld　metal　had　a　higher　yield　strength　and　ultimate　tensile　strength,　but　lower　ductility.　The　stress-strain　relations　of　the　base　metal　and　the　weld　metal　obtained　in　the　tests　can　be　well　fitted　by　the　modified　Ramberg-Osgood　equations.　The　differences　of　stress-strain　relation　between　base　metal　and　weld　metal　should　be　taken　into　consideration,　and　the　corresponding　constitutive　model　should　be　used　separately　in　the　accurate　load　capacity　analysis　of　welded　stainless　steel　connections.　©　2018,　Engineering　Mechanics　Press.　All　right　reserved.