An　experimental　study　of　the　ultralow-cycle　fatigue　of　iron-based　shape　memory　alloy　(Fe-SMA)　in　triaxial　stress　states　was　conducted.　Monotonic　tensile　tests　of　specimens　with　different　geometries　were　carried　out　to　investigate　monotonic　mechanical　properties　of　Fe-SMA　under　various　triaxial　stress　states　in　terms　of　stress　triaxiality　and　Lode　angle,　followed　by　ultralow　cyclic　tests　(cycles　＜100)　which　were　carried　out　to　study　the　ultralow-cycle　fatigue　of　Fe-SMA　under　various　loading　systems　at　triaxial　stress　states.　Fe-SMA　had　nonlinear　combined　hardening　under　cyclic　loading.　A　parameter　identification　method　based　on　an　optimization-based　algorithm　was　established　to　calibrate　the　constitutive　model　of　Fe-SMA.　The　initiation　and　propagation　of　cracks　in　the　fracture　process　were　different　for　Fe-SMA　under　monotonic　and　cyclic　loading.　The　influences　of　stress　triaxiality　and　Lode　angle　on　the　fracture　ductility　of　Fe-SMA　were　investigated.　An　ultralow　cyclic　fracture　criterion,　the　cyclic　Bai-Wierzbicki　(CBW)　criterion,　was　established　based　on　the　accumulation　of　ductile　damage　and　the　attenuation　of　ductile　damage　threshold.　The　applicability　of　the　calibrated　constitutive　model　and　the　proposed　fracture　criterion　was　validated　by　simulating　the　ultralow-cycle　fatigue　and　fracture　failures　of　Fe-SMA.