The　mixed　type　crack　is　common　to　be　found　in　engineering　practices,　however,　the　characteristics　of　mixed　I/II　creep　crack　tip　fields　have　not　been　studied　thoroughly.　The　aim　of　this　part　of　the　paper　is　to　study　the　dominance　of　C(t)-integral　for　mixed　I/II　type　creep　crack　tip　field　under　transient　creep.　The　boundary　layer　model　is　presented　to　investigate　the　dominance　of　C(t)　under　various　mixed　mode　cases.　For　transient　mixed　mode　creep　crack　under　boundary　layer　model,　C(t)-integral　is　related　with　the　effective　stress　intensity　factor　(SIF).　The　near　field　of　mixed　creep　crack　tip　field　can　be　influenced　by　the　remote　T-stress　greatly.　The　maximum　tangential　stress　direction　also　can　be　influenced　if　the　remote　T-stress　level　is　large　enough.　The　loss　dominance　of　the　C(t)　presents　more　remarkable　under　negative　stress　under　transient　creep.　The　relations　of　creep　mixity　factor　with　remote　elastic　mixity　factor　of　the　boundary　layer　model　is　also　presented.　The　T-stress　effects　on　the　constraint　parameter　Q＇　and　Q*　are　presented.　The　case　that　near　the　pure　mode　I　case　presents　the　most　significant　loss　of　constraint　compared　with　the　other　mixed　mode　cases.　The　comparison　between　the　sharp　crack　and　blunted　crack　is　made,　and　the　sharpening　effect　is　found　be　existed　in　the　pure　mode　II　case　which　reveals　that　the　situation　of　mode　II　case　may　have　a　more　severe　damage　process　than　that　of　mode　I　case.