String　stability　analysis　is　one　of　key　factors　to　understanding　traffic　flow　dynamics.　Cooperative　adaptive　cruise　control　(CACC)　vehicles　are　desired　to　enhance　stability　of　vehicular　flow　by　monitoring　multiple　vehicles.　From　the　perspective　of　mixed　traffic,　this　study　proposes　a　generalized　analysis　method　for　CACC　feedback　gains　to　achieve　stable　mixed　flow.　To　deal　with　this,　a　random　mixed　flow　is　divided　into　general　small　platoons,　in　which　one　tail　CACC　monitors　multiple　vehicles　ahead.　These　general　platoons　with　different　lengths　are　defined　as　connected　vehicular　systems.　Based　on　the　generalized　car-following　models,　transfer　function　theory　is　employed　to　derive　string　stability　criteria　that　can　keep　these　connected　vehicular　systems　stable　for　all　possible　vehicle　speeds.　A　case　study　is　also　carried　out　to　validate　usability　of　the　proposed　generalized　work.　The　proposed　generalized　method　is　applicable　to　various　car-following　models　and　large　connected　vehicular　systems,　thereby　helping　achieving　the　string　stability　enhancement　of　mixed　traffic　flow.　(C)　2021　American　Society　of　Civil　Engineers.