Aramid discontinue fiber (DCF) and aramid pulp (PPTA) were used to reinforce peroxide-cured hydrogenated acrylonitrile butadiene rubber (HNBR) filled with carbon black (N220) to obtain HNBR composites with high modulus and strength. The effects of type and dosage of fibers on the mechanical properties were studied. The results show the Mooney viscosity of HNBR/CB composites increases with increase of the content of DCF, but the dosage of PPTA has little effect on the Mooney viscosity of HNBR/CB composites. HNBR/CB/DCF vulcanizates show stronger filler-filler networks than HNBR/CB/PPTA vulcanizates. The strength and hardness of HNBR/CB/DCF vulcanizates are higher than those of HNBR/CB/PPTA vulcanizates.