Material　mismatch　effect　on　the　cracking　behavior　is　an　important　topic　for　those　welding　structures.　Characterization　of　the　material　constraint　effect　based　on　rigorously　asymptotic　solution　is　studied　in　this　paper.　Based　on　decomposition　of　the　second　order　term,　the　constraint　effect　characterization　parameter　is　decomposed　as　material　constraint　parameter　and　geometry　constraint　parameter.　In　general,　the　total　constraint　level　for　crack　tip　under　undermatch　condition　is　higher　than　overmatch　condition.　The　specimen　with　positive　biaxiality　could　lead　to　a　higher　constraint　level　compared　with　that　of　negative　biaxiality.　Geometry　constraint　effect　and　material　constraint　effect　could　not　be　separated　independently　from　rigorously　asymptotic　solution　for　those　cases　with　positive　biaxiality.　For　a　crack　tip　field　under　non-positive　biaxiality,　the　material　constraint　effect　can　be　characterized　independently　although　it　is　approximate.　For　these　conditions,　the　proposed　material　constraint　effect　and　geometry　constraint　effected　characterized　are　approximately　independent　on　material　mismatch　factor,　crack　depth　ratio　and　stress　biaxiality.　An　empirical　formula　has　been　presented　to　characterize　the　geometry　constraint　effect　and　material　constraint　effect　for　the　crack　tip　in　the　weldment　under　biaxial　loading,　which　has　been　verified　with　fine　accuracy.