The 2wt%CNTs/Al5083 composite powder was prepared by High Energy Milling, and the effect of the milling time on microstructure of the 2wt.%CNTs/Al5083 composite powder was investigated. The Microstructure was observed by SEM, TEM and XRD. The result showed that prolonging the milling time lead to the reduction of the Medium particle size D50. The best D50 was obtained at milling 2.5h with the particle size of 22.33μm. CNTs homogeneous embedded into the Al-matrix when the milling time was 2.5h. The average crystallite size of Al was 46.4nm after milling for 2.5h, and the average crystallite size of Al also increased as the recrystallization.