Fracture　failure　of　welding　joints　is　one　of　the　primary　forms　in　steel　structure,　and　fracture　prediction　can　provide　suggestions　and　guidance　for　engineering　applications.　To　predict　the　ductile　fracture　of　welded　joints,　the　Void　Growth　Model　(VGM)　and　the　Stress　Modified　Critical　Strain　Model　(SMCS)　based　on　the　microscopic　mechanism　were　studied.　The　tensile　tests　of　Q355　steel,　Q235　steel,　ER50-3　and　ER49-1　consumables　commonly　used　in　engineering　were　carried　out.　The　constitutive　models　of　four　materials　were　established　through　the　tensile　tests　of　standard　round　bar　specimens.　The　fracture　parameters　eta(mon)　and　gamma　of　base　metal,　weld　metal,　and　heat　affected　zone　were　calculated　through　the　tensile　tests　of　notched　round　bar　specimens　and　the　UVARM　(User　subroutine　to　generate　element　output).　Finally,　the　fracture　prediction　model　was　used　to　predict　the　fracture　of　the　thin-walled　steel　tube　beam-column　joints,　and　the　applicability　of　the　VGM　and　SMCS　models　was　discussed.　The　function　f(theta)　on　the　Lode　Angle　parameter　is　introduced　to　modify　the　VGM　model.　The　modified　fracture　prediction　model　was　used　to　predict　the　initial　fracture　of　beam-column　joints.