Biodiesel is regarded as one of the most promising alternatives for petroleum diesel. In this study, biodiesel continuous production with three kinds of reactor which are straight tube, coil and fixed bed reactor were compared, and the results showed that the fixed bed reactor needed a shortest stable time of 30 min, and with the condition of methanol to oil molar ratio 42:1, 18 MPa, 150 min and 300 degrees C, the highest yield: 80.11% of methyl ester was obtained. A continuous coupling process of supercritical extraction and non catalytic supercritical methanol transesterification method for preparing biodiesel is put forward. Based on the investigation of process optimization, oil extraction was found to be the crucial step for the coupling process. The optimum reaction condition was the extraction and reaction temperature 40 degrees C and 300 degrees C, pressure 18 MPa, and the flow rate of CO2 and n-hexane were 21/min and 0.4mlimin, respectively. In these circumstances, the fixed bed reactor provided a yield of 83.84%. (C) 2016 Elsevier B.V. All rights reserved.