In the present study,the transesterification of glycerol trioleate was carried out over a basic ionic liquid,1-butyl-3-methylimidazolium hydroxide ([Bmim]OH) and an 87.2％ yield of methyl ester was achieved.The product was isolated through simple decantation from the biphasic system due to the immiscibility of [Bmim]OH with ester.[Bmim]OH can be easily recovered and reused six times without dramatic decrease in ester yield.