The average molecular weight of bisphenol A-type epoxy resin has a significant effect on its performance. Consequently

two different degrees of polymerization of bisphenol A-type glycidyl ether（DGEBA） were mixed in different proportions by molecular dynamics simulation（MD）. The effects of different average molecular weights on the thermodynamic properties of epoxy resin system were studied using methyltetrahydrophthalic anhydride（MTHPA） as a curing agent

and compared with those of DGEBA/MTHPA system with polymerization degree of 0. The results show that

with the increase of average molecular weight

the glass transition temperature（Tg） of the system increases first and then decreases

but both are higher than those of the DGEBA/MTHPA system with a degree of polymerization of 0. The average molecular weight more remarkably affects the thermal expansion coefficient（CTE） of the rubber system. The elastic modulus of the system first rises and then decreases. When the average molecular weight is 700～750

the elastic modulus increases to the most extent.