In　order　to　study　the　shear　behavior　of　bonding　interface　between　engineering　cementitious　composites(ECC)　material　and　existing　concrete　as　well　as　the　action　mechanism　of　shear　load,　three　groups　of　Z-shape　direct　shear　specimens　with　joints　and　one　group　of　whole　cast-in-place　contrast　specimens　were　designed　and　tested.　The　effects　of　different　reinforcement　ratios　and　treatment　methods　of　joints　on　shear　strength,　load-slip　curve,　steel　strain　and　shear　strength　of　joints　were　investigated　and　compared.　The　results　show　that　the　shear　bearing　capacity　of　ECC-concrete　interface　is　stronger　than　that　of　ordinary　concrete　under　shear　load,　the　shear　bearing　capacity　of　specimens　treated　with　keyway　is　higher　than　that　of　rough　surface.　The　shear　bearing　capacity　of　specimens　is　determined　by　the　interfacial　bonding　force　and　boundary.　The　higher　the　reinforcement　ratio　is,　the　smaller　the　proportion　of　interfacial　bonding　force　is.　The　calculation　method　proposed　can　calculate　the　shear　capacity　and　reflect　the　variation　of　its　components　with　slip.　©　2020,　Editorial　Department　of　Journal　of　Building　Materials.　All　right　reserved.