Esterification reaction of lactic acid with butanol catalysed by Amberlyst-type ion exchange resin was carried out in a batch reactor under the temperature range of 80~100 ℃. The rection rate was significantly influenced by water contents (wt%), alcohol/LA mole ratio, and continuously reaction temperature. The inhibiting effect of water and butanol has been evaluated. Esterification of the alctic acid with butanol is promoted by removing residual water.