Four novel Bronsted acidic ionic liquids were synthesized and characterized by FT-IR, H-1 NMR and C-13 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). (C) 2016 Elsevier B.V. All rights reserved.