Fully　ceramic　microencapsulated　(FCM)　fuel　is　a　promising　ATF　concept　with　extraordinary　fission　product　inclusion　capacity,　excellent　oxidation　and　corrosion　resistance,　and　high　thermal　conductivity.　The　thermo-mechanical　performances　are　of　great　significance　when　evaluating　the　safety　and　applicability　of　a　nuclear　fuel.　In　this　study,　a　finite　element　method　(FEM)　model　for　FCM　thermo-mechanical　performances　analysis　was　presented.　The　thermo-mechanical　behaviors,　coupled　with　irradiation　behaviors　(including　irradiation-induced　dimensional　change　(IIDC),　heat　generation,　conduction,　thermal　expansion,　creep,　burnup,　and　gap/plenum　pressure,　etc.),　were　developed　to　investigate　the　thermal　and　mechanical　characteristics　of　TRISO-based　FCM　Fuel.　A　simplified　model　of　TRISO　fuel　particles　was　established　and　validated.　After　that,　a　full　3D　modeling　of　FCM　fuel　pellet　with　typical　packing　fractions　was　realized　by　an　optimized　stochastic　strategy.　A　numerical　method　was　validated　and　successfully　applied　to　realize　the　simulations　of　a　FCM　fuel　pellet.　Two　different　thermal　boundaries,　namely　fixed　particle　power　and　fixed　pellet　power,　were　performed　to　investigate　the　irradiation　behavior　of　FCM　fuel.　Moreover,　the　effects　of　burnup,　particle　spacing,　no　fuel　zone　width　and　other　key　parameters　were　well　studied　and　investigated.　The　performed　calculation　showed　that　temperature　and　stress　in　matrix　and　TRISO　are　both　positively　correlated　with　the　packing　fraction.　It＇s　worth　noting　that　compared　with　the　cases　of　fixed　particle　power,　cases　of　fixed　pellet　power　may　lead　to　higher　fuel　temperature　and　higher　stress.　The　results　also　implied　that　from　the　perspective　of　probability　evaluation,　most　of　the　TRISO　particles　in　FCM　fuel　can　maintain　the　structural　integrity　under　different　packing　fractions,　but　some　of　the　particles　with　higher　stress　may　crack　or　damage,　especially　in　the　cases　of　high　burnup　and　high　packing　fraction.　©　2021