The cure kinetics of epoxy system modified with CTBN were studied by isoconversional expression. The maximum exothermic peak value of DSC thermogram increased with the increment of heating rate. By the integration of DSC thermograms, the conversion vs. temperature curves shifted to right-hand side with the increment of heating rate. From the .slope of straight lines, the activation energy could be calculated and they were in the range of 54,39∼56.94 kJ/mol.