In　this　work,　biodegradable　antimicrobial　cationic　copolyesters　were　prepared　via　a　simple　two-step　process.　Firstly,　brominated　poly(butylene　succinate)　(BPBS)　was　prepared　by　addition　of　bromine　to　carbon　carbon　double　bonds　on　the　backbone　of　poly(butylene　succinate-co-butylene　fumarate)　(PBSF).　Then,　the　quaternization　of　BPBS　with　series　of　N,N-dimethyl　alkylamines　afforded　poly(butylene　succinate)　containing　quaternary　ammonium　cations　(QPBS)　with　various　ion　contents　and　alkyl　chain　lengths.　The　structures　of　BPBS　and　QPBS　were　systematically　characterized　by　NMR,　ATR-FTIR,　GPC　and　XPS.　The　hydrophilicity　and　the　antibacterial　activity　have　been　studied　by　water　contact　angle　(WCA),　inhibition　zone　method,　optical　density　method　and　scanning　electron　microscope　(SEM).　WCA　test　indicates　that　the　hydrophilicity　of　polyester　is　greatly　improved　after　the　introduction　of　quaternary　ammonium　cations.　The　antibacterial　study　reveals　that　cationic　copolyesters　exhibited　excellent　antibacterial　performance　for　both　S.　maws　and　E.　coil　when　the　alkyl　chain　length　was　greater　than　8,　as　compared　with　the　ion　content　and　alkyl　chain　length　is　a　more　important　factor　for　the　antibacterial　performance.　Considering　the　biodegradation,　good　antibacterial　activities　and　simple　process,　this　kind　of　material　may　have　great　potential　to　be　applied　as　biomaterials.