Nitrile rubber (NBR) was reinforced by poly(p-phenylene terephthalamide) (PPTA) with a coprecipitation method from a common solvent of them. PPTA was converted to N-sodium PPTA with sodium hydride in DMSO, forming homogeneous solution. DMF dissolves NBR. Both solutions were blended to form an isotropic solution. The precipitant was NBR reinforced by PPTA which was regenerated from N-sodium PPTA at coagulation as reported previously. The molecular composite thus obtained was mill-blended with poly(vinyl chloride) (PVC) in order to enhance solvent resistant property. The vulcanized composite of NBR/PVC reinforced by PPTA showed higher modulus, higher strength and more improved solvent resistance than the gum stock and the black stock of NBR/PVC. The properties of the molecular composite containing 5phr PPTA found approximately comparable to those of the black stock of NBR/PVC with 30–40phr ISAF carbon black.