Abstract: The influences of aramid fiber (AF) on the fatigue behavior of AF reinforced styrene butadiene rubber filled with carbon black composites (AF-CB/SBR) were researched. Under the stress control condition, the fatigue life of notched specimens can be improved 25.5 times with the help of the addition of a small amount of AF. The storage modulus of the rubber samples decreases after the fatigue process and AF in this system can decrease the ratio of G₀' and G₁₀₀' (G₀'/G₁₀₀') to 10.5%, indicating lower Payne effect compared with the one without AF. The complex modulus decreases with the increase of fatigue cycles, while higher complex modulus can be remained in the composites which contain a small amount of AF than the one without AF. The complex modulus of AF-CB/SBR composite was 1.73 times as that of CB/SBR system even if the fatigue cycles have reached to 30000. The stretching stress at 100% and 300% of fatigued sample increases first and then reduces with the increasing of fatigue progress, while the elongation at break decreases. Relative to the deformation, fiber reinforcement has a hysteresis effect, and the relative interfacial slip energy decreases with the increase of fatigue strain amplitude; SEM photos exhibite a certain extent stripping of the rubber matrix and the interface between fiber and rubber is destroyed after the fatigue process.