Ct　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　Ct　for　weld　creep　cracks.　Simulation　results　showed　that　Ct　of　weld　interface　cracks　could　be　estimated　by　Yoon’s　method.　For　weld　non-interface　cracks,　Ct　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.　©　2016　Informa　UK　Limited,　trading　as　Taylor　&　Francis　Group.