Abstract: A crosslinked nitrile-butadiene rubber (NBR)/hindered phenol composite was successfully prepared by mixing tetrakis (methylene-3-(3-5-ditert-butyl-4-hydroxy phenyl) propionyloxy) methane (AO-60) into NBR. The microstructure of the NBR/AO-60 composite was characterized by DSC, SEM, XRD and DMTA, and its thermal and dynamic mechanical properties were studied. The results show that the pure AO-60 is a crystalline material, but in the hindered phenol/NBR composites most of the AO-60 molecules are amorphous and form AO-60 domains. In the case of NBR/AO-60 composites, large numbers of hydrogen bonds are formed not only in the AO-60 molecules within AO-60-rich domains but also between NBR and AO-60 molecules. The dissociation of the intermolecular hydrogen bonds leads to the appearance of two novel transitions above the glass transition temperature of the matrix NBR. It was found that it is a good damping material because of the novel dynamic mechanical property of the NBR/AO-60 composites.