The　high-temperature　fracture　parameter　C-t　is　an　important　parameter　that　is　used　to　predict　the　service　life　and　assess　the　safety　of　high-temperature　structures　in　the　entire　creep　stage.　Therefore,　it　is　necessary　to　investigate　the　effect　of　threshold　stress　on　this　parameter.　In　this　paper,　the　effect　of　the　threshold　stress　on　C-t　has　been　investigated　using　the　Finite　Element　Method　(FEM)　for　9-12　wt-%　Cr　steels.　For　all　the　cases　that　were　simulated　the　power-law　creep　exponent　n　was　fixed　at　5;　this　was　because　n　is　usually　equal　to　5　for　the　Chromium　steels.　The　results　of　the　FEM　simulations　showed　that　C-t　was　significantly　affected　by　threshold　stress.　Based　on　the　results　of　the　FEM,　a　parameter　was　then　introduced　into　the　equation　for　estimating　C-t　in　order　to　calculate　the　effect　of　the　threshold　stress.　The　results　showed　that　was　constant　when　there　was　no　threshold　stress,　but　that　its　value　increased　as　the　threshold　stress　and　the　power-law　creep　coefficient　A　increased.　The　effect　A　had　on　was　negligible　when　A　was　smaller　than　1E-19　MPa-n/h.　In　addition,　decreased　as　both　the　value　of　A　and　the　threshold　stress　increased.　It　was　also　found　that　and　decreased　slightly　as　the　level　of　C*increased.