Four　novel　Brønsted　acidic　ionic　liquids　were　synthesized　and　characterized　by　FT-IR,　1H　NMR　and　13C　NMR　for　the　first　time.　Their　catalytic　activities　for　the　synthesis　of　biodiesel　via　the　transesterification　of　coconut　oil　and　methanol　were　investigated.　Among　all　the　tested　ionic　liquids,　[CyN1,1PrSO3H][Tos]　performed　best,　and　its　catalytic　performance　was　systematically　explored　by　orthogonal　experiment　based　on　the　single　factor　experiment.　The　results　show　that　the　order　of　factors　on　the　yield　of　biodiesel　is　reaction　temperature,　molar　ratio　of　methanol/oil,　catalyst　dosage　and　reaction　time.　The　maximum　biodiesel　yield　of　98.7%　was　obtained　under　the　optimal　reaction　conditions.　There　was　no　significant　decrease　of　its　catalytic　activity　after　being　reused　for　five　successive　cycles.　The　refined　biodiesel　meets　the　European　biodiesel　standard　(EN　14214).　©　2016　Elsevier　B.V.