Abstract: The cure reaction kinetics of E-51 epoxy resin and 4,4’-diaminodiphenylsulfone(DDS) system was investigated by the isothermal DSC method, and isothermal curing kinetics parameters at 170, 180, 190, 200 ℃ were obtained through fitting between the experimental data and the curing model. According to the values of coefficient of determination (R²) of the fitted data, a suitable curing reaction kinetic model was determined. The reaction process shows to be dominated by different mechanism at different stages of the E-51/DDS system curing process, when the cure degree is less than 40%, the curing system is Kamal autocatalytic reaction model; when the cure degree is more than 40%, the curing system is nth order reation model, with an initial autocatalytic reaction shifting into an nth order reaction as the reaction proceeding.