Carbon nano-tubes (CNTs) reinforced 7075 aluminum alloy matrix composite was prepared by friction stir processing, and the microstructure and fatigue properties of the composite were investigated. The results show that the grain size of the composite is much finer and MWCNTs (multi-walled carbon nano-tubes) are uniformly distributed in matrix material. Along with the increase of volume fraction of MWCNTs, the dispersion becomes worse and the fatigue property of the composite is higher than that of the annealed 7075 aluminum alloy matrix. Meanwhile, the fatigue property increases with the increase of MWCNTs content, but the tensile strength decreases gradually. Defects of large size intermetallics, non-metallic inclusion and chip-like metal oxide are observed in the composite which could strongly reduce the fatigue of the composite.