The curing reaction of bisphenol A epoxy resin and isocyanate was carried out and the curing mechanism was investigated.Differential scanning calorimetry(DSC)and Fourier transform infrared spectroscopy(FTIR)were used to monitor and analyze quantitatively the decrease of the groups of isocyanate，epoxy group and generation of new groups of isocyanurate and oxazolidone.The DSC results showed that three reactions mainly occurred during the curing process of epoxy/isocyanate system corresponding to three exothermic peaks.The FTIR results indicated that when reaction temperature was below 140℃ trimerization of isocyanate groups into isocyanurate was observed；when temperature was up to 200℃ the formation of oxazolidone ring by the reaction between epoxy and isocyanate occurred；when temperature was above 230℃ the transformation reaction of isocyanurate with epoxide group to oxazolidone occurred.The curing reaction time dependence of the conversions of epoxide，isocyanate，isocyanurate，oxazolidone groups at different temperature were studied.