The key properties of PMDA/ODA polypyromellitimide were simulated by method of molecular dynamics simulation.The results show that the polymer model was in the dynamic equilibrium state after a simulation of 298 K,200 ps NVT and NPT and the glass transition temperature was 606.5 K.The movement of polymer molecular segments become more active and the free volume decreased as the simulation temperature raising,that resulting in the cohesive energy density decreased gradually.The Young's Modulus,Shear Modulus,Volume Modulus and Poisson’s ratio was calculated as 5.12 GPa,1.87 GPa,6.44 GPa and 0.37 at 298 K,respectively.The conclusion were consistent with the experimental results,indicating that the molecular dynamics simulation method could be used to predict the properties of polyimide polymers.