Three types of aramid fibers (AFs) with various surface fibrillation degrees were introduced into nitrile rubber (NBR) matrix to prepare the AF/NBR composites, respectively. Their impacts on the mechanical and tribological performances of the NBR composites were mainly studied. The results showed that, as the fiber content increased, the tensile strength of the AF/NBR composites increased after initially decreased, and the turning point moved toward the direction of lower AF content with the fiber fibrillation degree increase. In