C-t　is　an　important　parameter　in　predicting　creep　crack　growth　life　from　the　small-scale　creep　stage　to　the　extensive　steady　state　creep　stage.　In　this　paper,　weld　interface　and　non-interface　creep　cracks　for　compact　tension　(CT)　specimens　with　heat-affected　zone　(HAZ)　were　studied　by　finite　element　method　(FEM)　to　systematically　research　the　estimation　method　of　C-t　for　weld　creep　cracks.　Simulation　results　showed　that　C-t　of　weld　interface　cracks　could　be　estimated　by　Yoon＇s　method.　For　weld　non-interface　cracks,　C-t　under　the　small-scale　and　transition　creep　stages　could　be　exactly　estimated　by　a　proposed　method.　The　accuracy　of　the　proposed　method　was　not　affected　by　HAZ,　but　Yoon＇s　method　was　slightly　affected　by　HAZ.