The physical aging process of 4,4’-diaminodiphenylsulfone (DDS) cured diglycidyl ether bisphenol-A( DGEBA) blended with poly( ether sulfone) (PES) was studied by differential scanning calorimetry (DSC) at four aging temperatures between T-g-50 degrees C and T-g-10 degrees C. At aging temperatures between T-g-50 and T-g-30 degrees C, the experimental results of epoxy resin blended with 20 wt % of PES showed two enthalpy relaxation processes. One relaxation process was due to the physical aging of PES, the other relaxation process was due to the physical aging of epoxy resin. The distribution of enthalpy relaxation process due to physical aging of epoxy resin in the blend was broader and the characteristic relaxation time shorter than those of pure epoxy resin at the above aging temperatures (between T-g-50 and T-g-30 degrees C). At an aging temperature between T-g-30 and T-g-10 degrees C, only one enthalpy relaxation process was found for the epoxy resin blended with PES, the relaxation process was similar to that of pure epoxy resin. The enthalpy relaxation process due to the physical aging of PES in the epoxy matrix was similar to that of pure PES at aging temperatures between T-g-50 and T-g-10 degrees C.