In the present study, the kinetics of transesterification of palm oil was explored under conventional heating and microwave irradiation, using CaO as heterogeneous catalyst. The optimal experimental conditions were, microwave power of 150 W, alcohol to oil molar ratio of 9: 1, catalyst of 5%, stirring speed of 450 r/min and reaction time of 60 min. By establishing kinetic models, the total reaction orders of transesterification under the two heating methods were figured out. The total reaction order under conventional heating was 1, while 3 under microwave irradiation, which indicated that microwave irradiation could increase the overall reaction order and accelerate the conversion rate for biomass to biodiesel. (C) 2016 Elsevier Ltd. All rights reserved.