Twaron aramid fibers (AFs) were modified by atmospheric air dielectric barrier discharge plasma with various parameters. The wettability of plasma-treated AF was observed by means of contact angle and surface free energy measurement. Surface roughness was investigated with the help of scanning electron microscopy. Energy-dispersive X-ray analysis was used to measure the chemical composition of AF in volume with one micrometer dimension. The tensile test of AF roving was carried out to determine the effect of plasma surface treatments on the mechanical properties of the fibers. A pull-out force test was carried out to observe the adhesion effect with matrix material. Lower contact angles, increase of oxygen concentration at the fiber surface, surface roughness and increase of pull-out force with the rubber matrix were observed after the air plasma treatment.