A methed of Comparative DSC technique is proposed for physical aging study. The essential of the comparative DSC technique consists of comparing the enthalpy relaxation behavior of aged sample with quenched sample as a reference. The accuracy of comparison is improved because of simultaneous measure of the sample and reference which makes noise of the apparatus subtractive. The technique has been applied to study the influence of crosslinking on the enthalpy relaxation behavior of epoxy resins. Effect of cross-linking on the kinetics of enthalpy relaxation of epoxy resins are obta-ined and discussed.