The　Y-joints　between　prefabricated　shield　tunnel　lining　segment　and　cast-in-place　main　structure　of　station　are　the　mechanical　weaknesses　of　the　station　structure　by　expansion　of　parallel　shield　tunnels.　The　static　tests　on　Y-joints　of　1　∶　1　scale　were　conducted　to　study　the　mechanical　behavior　and　failure　mechanism　of　the　joints.　The　concrete　strain,　steel　strain,　damage　pattern　and　damage　mechanism　of　two　types　of　Y-joints　were　studied　under　the　horizontal　and　vertical　loads.　The　results　showed　that　the　shear　capacity　of　Y-joints　can　be　strengthened　with　the　shear　key　wielded　on　the　steel　plate.　The　shear　key,　however,　has　a　strong　restraint　effect　on　the　lower　part　concrete　of　the　lining　segment.　As　a　result,　the　lining　segment　stiffnesses　of　upper　and　lower　part　differ　greatly,　and　the　ability　of　the　joint　in　resisting　external　forces　is　greatly　reduced.　The　failure　mechanisms　of　the　two　types　of　Y-joints　are　different.　The　failure　of　the　joint　of　type　A　is　mainly　caused　by　the　crushing　of　concrete　at　the　lower　part　of　the　segment　which　shall　be　the　compression　failure　of　concrete.　The　failure　of　the　joint　of　type　B　is　mainly　caused　by　the　tensile　cracking　of　the　upper　part　of　the　segment　concrete　which　shall　be　the　tensile　failure　of　concrete.　Both　the　two　types　of　Y-joints　in　this　test　can　meet　the　requirements　of　strength　and　deformation　of　the　station　structure　by　expansion　of　parallel　shield　tunnels.　Furthermore,　some　measures　for　the　Y-joint　are　put　forward　here　to　improve　the　mechanical　performance　of　the　structure.　©　2022　Editorial　Office　of　China　Civil　Engineering　Journal.　All　rights　reserved.