Wire-brushing is used for different purposes such as removing metal surfaces oxides, increasing surface brightness, improving fatigue properties and surface activation before coating. The wire-brushing severely scratches and stirs the metals in the surface layers, so that complicated metal flow gives rise to very large amount of plastic strain and increases dislocation density of the surface layer. After recovery, subdivided grains and a nanocrystalline structure are formed on the surface. Formation of nanocrystalline structure on the surface of Al 6061 alloy by wire brushing at various brushing speeds was investigated by using atomic force microscopy and X-ray diffraction. The results showed that the severe plastic deformation decreased the surface grain size to 30-70 nm.