As　one　of　the　new　advanced　fuels　proposed　to　improve　the　safety　of　nuclear　reactors,　fully　ceramic　microencapsulated　(FCM)　fuel　consisting　of　TRistructural　ISOtropic　(TRISO)　particles　dispersed　in　a　silicon　carbide　matrix　has　received　a　lot　of　attention　at　home　and　abroad　because　of　its　distinguished　advantages　such　as　high　corrosion　resistance　and　excellent　fuel　irradiation　stability.　For　analyzing　FCM　fuel　performance　and　optimizing　FCM　fuel　design,　it　is　necessary　to　assess　complicated　behaviors　of　TRISO　particle　fuel　under　irradiation.　To　investigate　the　multidimensional　behavior　of　TRISO　particle　fuel　with　UN　or　UO2　kernel,　a　three-dimensional　thermomechanical　coupling　model　was　developed　based　on　multiphysics　coupling　finite　element　software　COMSOL.　Additionally,　thermomechanical　performance　analysis　of　TRISO　particle　fuel　with　irradiation-dependent　material　properties　and　behavior　models　was　conducted,　and　important　phenomena　were　implemented　such　as　fission　gas　release,　production　and　diffusion　of　CO　gas,　as　well　as　the　evolution　of　particle　radius　due　to　the　irradiation　deformation,　fission　product　swelling　strain　and　irradiation　creep.　Moreover,　on　the　basis　of　the　preliminary　thermomechanical　analysis,　the　performance　of　TRISO　particle　fuel　with　UO2　and　UN　kernel　were　compared.　This　paper　is　intended　as　an　exploratory　investigation　of　TRISO　fuel　behavior,　which　will　provide　vital　reference　for　further　performance　analysis　and　design　optimization　of　subsequent　FCM　fuel.　©　2022　by　ASME.