explained by the fact that, a high temperature is required to help 75% ethanol, n-hexane and sulfuric acid disrupt the cell walls as well as accelerate the transesterification reaction. The effect of reaction time was showed on Table 1. The reaction time up to 2.0 h could increase biodiesel yields to approach 90.18%, but the yield decreased when the reaction was continued for up to 2.5 h. The Transesterification reaction is a reversible reaction, and too long the reaction time enhances reverse reaction, thereby reducing the product yield. In this work, sulfuric acid was selected as the direct transesterification reaction catalyst because of the free fatty acid in the microalgae lipids. It is clear that the FAEE yield increased significantly with catalyst volume rising from 0.2 mL to 0.6 mL (Table 1). However, there was almost no increasing in biodiesel yield when the catalyst volume exceeded 0.6 mL. In conclusion, with the reaction condition that hexane to 75% ethanol ratio 1:2, solvent dosage 6.0 mL, reaction temperature 90 C, reaction time 2.0 h and catalyst volume 0.6 mL, the conversion yield of the direct transesterification can reach 90.02 ± 0.55 wt.%.