Most　of　the　current　methods　for　estimating　the　shear　contribution　of　CFRP　are　based　on　laboratory　testing　of　small-sized　specimens.　The　applicability　of　the　current　codes　on　large-sized　FRP-strengthened　shear　walls　remains　debatable.　The　present　study　addresses　the　problem　by　investigating　the　combined　effects　of　structural　sizes　and　CFRP　ratios　on　the　shear　contribution　of　CFRP.　Through　experiments,　a　series　of　geometrically　similar　CFRP-strengthened　RC　shear　walls　were　designed　and　subjected　to　a　cyclic　horizontal　loading.　From　the　experiments,　the　following　results　can　be　obtained.　The　application　of　the　externally　bonded　CFRP　strips　alters　the　failure　mode　and　enhances　remarkably　the　seismic　resistance　by　suppressing　crack　propagation　and　increasing　the　energy　dissipation.　The　increasing　specimen　size　reduces　the　enhancement　effects　of　CFRP　on　the　nominal　shear　strength,　ductility,　and　energy　dissipation.　These　findings　indicate　that　without　considering　the　size　effect,　the　effective　strain　that　reflects　the　shear　contribution　of　CFRP　strips　are　greatly　overestimated　by　the　current　codes.　Therefore,　the　present　study　proposed　and　validated　an　effective　strain　factor　capturing　the　combined　effects　of　the　structural　size　and　the　CFRP　ratio　on　the　shear　contribution　of　CFRP　strips,　serving　in　assessing　the　shear　strengthening　effect　of　CFRP　on　shear　walls.