The　low　yield　point　(LYP)　steel　components　for　energy　dissipation　generally　experiences　substantial　plastic　deformation　at　triaxial　stress　states　before　fracture　failure.　This　paper　presents　experimental　and　theoretical　studies　on　the　ultra-low　cyclic　fatigue　performance　of　LYP　at　triaxial　stress　states.　The　monotonic　mechanical　properties　of　LYP　steel　under　triaxial　stress　states　are　established　through　14　tensile　tests　on　four　types　of　specimens　with　different　initial　geometries.　Subsequently,　10　ultra-low　cyclic　tests　are　conducted　to　investigate　the　ultra-low　cycle　fatigue　behavior　of　LYP　steel　at　various　triaxial　stress　states.　An　optimization-based　technique　is　employed　to　calibrate　the　constitutive　model　for　LYP　steel,　incorporating　both　isotropic　and　kinematic　hardening　performances.　A　phase-field　framework　is　established　and　used　for　fracture　prediction　of　LYP　steel　loading　at　triaxial　stress　states.　In　this　proposed　framework,　the　critical　fracture　density　representing　the　fracture　toughness　in　phase-field　theory　is　taken　as　a　variable　related　to　equivalent　plastic　strain　and　stress　states　rather　than　a　constant　to　describe　the　variation　of　fracture　ductility　of　material　under　cyclic　loading.　The　calibrated　constitutive　model　and　proposed　fracture　prediction　framework　are　both　implemented　in　finite　element　model　and　validated　by　simulating　experimental　results.　©　2024　Elsevier　Ltd