The curing process of 123 resin was studied by means of microcalorimetry with diethyl sulfate as a curing agent. The results show that the acid value( greater than l percent) of diethyl sulfate has an effect on the curing rate and cured degree. When acid values of diethyl sulfates vary in a proper range ( less than l percent) ,curing rate,cured degree and curing heat of 123 resin will not be affected. The cu- ring mechanism of 123 resin was studied through FTIR technique. It shows that with the deepening of cured degree,the magnitude of characteristic peaks of >C=C< at 1 651 cm ^-1. =CH₂ at 3 095 ~3 075 cm ^-1 and 3 040 ~ 3 010 cm ^-1 attenuates sharply,indicating that the cross-link reaction takes place on the non-saturated double bond within the >C=C< group for monomers Ⅰ and Ⅱ.