We have proposed a novel DSEC (direct saponification-esterification conversion) strategy that could directly disrupt cells and convert lipid into biodiesel efficiently in a single vessel under the conditions of high water and fatty acid. It is advantageous at least for several reasons. First of all, DSEC eliminates lipid extraction and purification steps in the conventional process, which usually accounts for more than half of production cost. Secondly, compared with the alkali catalyzed transesterification process, DSEC completely alleviated the restriction of incapable of dealing with high content of water and free fatty acid. Thirdly, the required reaction time would be a fraction of traditional acid transesterification and similar to, if not better, traditional alkaline transesterification. In this study, both Chlorella sp. ESP-6 and Rhodotorula glutinis were used as raw materials for biodiesel production to investigate and verify DSEC kinetics. With the consideration of lipid content variation, the mechanisms were confirmed and same kinetic parameters could be obtained for both yeast cells and microalgae except cell disruptions and esterification. The difference in cell disruption parameter would be obvious due to the rigidity of cell wall of microalgae compared with yeast cells. And the difference of esterification constants may be due to different carbon length of fatty acids (the average molecular weight 283 for Chlorella and 291 for Rhodotorula) and different degree of saturation. However, in both cases, our proposed mechanism were satisfactorily confirmed and the kinetic parameters with good fitting against experimental data were obtained successfully.