To study the effect of polybutadiene rubber (BR) binder on the performances of RDX-based pressed polymer bonded explosive (PBX), the mass, volume, the vacuum stability, mechanical performances and mechanical sensitivities of grain before and after aging were measured by high temperature accelerated aging test at 71 ℃. The change situation of microstructure, elemental content and chemical environment of the explosive was observed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that after high temperature storage, change rate of volume and mass of grain is less than 1%, and no obvious defects such as crack are observed. The compressive strength increases by 74% and tensile strength increases by 117%. The impact sensitivity decreases from 8% to 4%, and the friction sensitivity decreases from 18% to 8%. The stability of the explosive does not change significantly in the high temperature aging process. The analysis thinks that in the accelerated aging process, due to the instability of carbon-carbon double bond, BR binder in the grain occurs oxidative crosslink, making the crosslinking degree increase, and the softening, spreading and uniform distribution caused by heating make the effect of coating and binding enhance, thereby, the mechanical performance of the explosive is improved and the mechanical sensitivity is reduced.