In order to characterize the low temperature relaxation of epoxy resin modified with aromatic polyester, thermally stimulated current (TSC) and relaxation map analysis (RMA) were investigated. Two relaxation peaks at around -85 and 70 degrees C were observed as the indication of beta-relaxation of epoxy resin and T-g of polyester, respectively. The unknown peak of ESE-102 at around 20 degrees C was observed due to dipole orientation. The RMA data was showed that compensation temperature (T-c) and degree-of-disorder (DOD) were increased with increasing the concentration and the molecular weight of polyester, whereas the compensation time (tau(c)) was decreased. It can be concluded that the cooperative molecular motion in cured epoxy resin was more active as the concentration and the molecular weight of polyester increase.