Multiaxial　tests　were　performed　on　150　mm　3　150　mm　3　150　mm　cubic　specimens　of　three　strength　grades　of　plain　structural　recycled　aggregate　concrete　(RAC)　at　different　stress　ratios　using　a　large　static-dynamic　true　triaxial　machine.　Friction-reducing　pads　(two　layers　of　plastic　membrane　with　lubricants)　were　placed　between　the　compressive　loading　plate　and　the　specimens.　The　tensile　loading　planes　of　the　concrete　samples　were　processed　by　an　attrition　machine　and　then　the　samples　were　glued　to　the　loading　plate.　The　characteristic　failure　modes　of　the　specimens　and　the　crack　directions　were　observed.　The　three　principal　static　strengths　in　the　corresponding　stress　state　were　measured.　The　influence　of　the　stress　ratios,　stress　states　and　strength　grade　on　the　triaxial　strengths　of　RAC　was　also　analysed.　The　experimental　results　showed　that　ratio　of　triaxial　failure　strength　sigma(3f)　to　the　corresponding　uniaxial　compressive　strength　f(c)　for　the　three　strength　grades　of　RAC　was　higher　than　that　of　conventional　concrete　(CC),　especially　under　triaxial　compression;　moreover,　it　is　dependent　on　the　strength　grade　of　RAC,　the　stress　states　and　stress　ratios;　however,　the　differences　of　tensile-compressive　ratios　between　the　RAC　and　CC　are　not　significant.　On　this　basis,　a　new　failure　criterion　with　the　six　parameters　is　proposed　for　plain　RAC　under　multiaxial　stress　states.　It　provides　the　experimental　foundations　for　strength　analysis　of　RAC　structures　subject　to　complex　loads.