The　printing　ink　on　the　plastic　surface　greatly　reduces　the　quality　of　recycled　plastic　products.　In　this　work,　quaternary　ammonium-modified　waste　cooking　oil　(WCOQE)　was　fabricated,　using　waste　cooking　oil,　epichlorohydrin　and　trimethylamine　aqueous　solution　as　raw　materials,　by　ring-opening　esterification　and　quaternary　amination　reaction.　The　synthesis　conditions　of　WCOQE　were　optimized,　and　the　structure　and　properties　of　WCOQE　were　characterized　by　FTIR,　zeta　potential　and　1H　NMR.　Furthermore,　WCOQE　had　excellent　emulsifying　performance,　low　kraft　point,　low　CMC　value,　good　foaming　and　stability,　which　could　effectively　reduce　the　surface　tension　of　water,　showing　application　potential　in　the　field　of　plastic　deinking.　Importantly,　compared　with　the　waste　cooking　oil　without　deinking　effect,　the　WCOQE　had　an　excellent　deinking　performance　on　the　ink　on　plastic　surface,　and　the　deinking　efficiency　could　be　improved　by　increasing　the　concentration　of　deinking　agent,　the　deinking　temperature,　and　prolonging　the　pre-soaking　and　stirring　time.　The　results　of　AFM,　EDS,　optical　photos　and　Leica　microscope　showed　that　the　roughness　changed　significantly,　and　the　ink　molecules　were　gradually　peeling　off.　This　work　highlighted　the　excellent　potential　of　quaternary　ammonium-modified　waste　cooking　oil　for　the　removal　of　printing　inks　on　the　plastic　surface.　©　2021　Informa　UK　Limited,　trading　as　Taylor　&　Francis　Group.