Abstract: A series of BTDE/PMDE copolymer PMR resin was synthesized by introducing a second monomer to PMR-15 system on the principle that material properties depend on its molecular structure. The relations between properties such as resin viscosity, impact strength and thermo-oxidative stability and molecular structure were discussed. Simultaneously, the optimal resin system was characterized by TGA, DSC and DMTA. Experiment shows that with increasing of the molecular weight, the resin viscosity and thermo-oxidative stability increase, while the impact strength decreases after increasing. With increasing of PMDE content, the resin viscosity and impact strength decrease, while the thermo-oxidative stability increases.