Evaluation　of　the　creep　crack　growth　is　very　important　for　predicting　the　life　of　high　temperature　structures.　Since　C-t　can　uniquely　characterize　creep　crack　growth　from　the　small　scale　creep　stage　to　the　extensive　steady　state　creep　stage,　an　engineering　estimation　method　of　C-t　was　proposed　for　a　crack　located　in　the　weld　with　mismatched　material　properties　between　the　base　material　and　the　weld　material　based　on　the　simulation　results　of　compact　tension　specimens.　For　the　crack　located　in　the　center　of　welding　seam,　C-t　was　estimated　by　the　proposed　method　under　the　small　scale　creep　stage　and　by　the　reference　stress　method　under　the　extensive　steady　state　creep　stage;　in　this　way,　C-t　was　estimated　under　the　whole　creep　stage.　The　estimated　results　agreed　well　with　the　simulation　results　if　the　width　of　welding　seam　of　h　was　no　smaller　than　the　size　of　the　stress　intensity　factor　dominance　zone.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.