Abstract: The sub/supercritical methanol were used for preparation of biodiesel fuel through alcoholysis of vegetable oils. The reaction conditions were optimized by orthogonal test. The influence of promoter on the transesterification reaction was investigated. The results show that the effect of reaction conditions without promoter on the yield of vegetable oil methyl ester has the following order: LHSV > temperature > alcohol/oil mole ratio > pressure. The addition of promote can significantly lower the reaction temperature and pressure and increase space velocity, and can produce the qualified biodiesel fuel in line with the national standared BD100（GB/T 20828-2007） under these mild conditions.

Key words: biodiesel, vegetable oils, alcohol, transesterification