Abstract: Aluminum/amorphous hydrogenated carbon (Al/a-C:H) nanocomposite thin films were deposited on silicon p (100) wafer and stainless steel substrates by magnetron sputtering of aluminum in an argon and methane atmosphere with different Al target power. The composition, microstructure, mechanical and tribological properties of composite films were systemically investigated by HR-TEM, XPS, nano-indenter and tribo-tester. The results show that the Al nanocrystallites could be easily formed in the amorphous carbon matrix, the sp2 hybrid carbon was increased as the Al was embedded into the films, and Al-doping could relax the internal stress whilst keeping high hardness of as-deposited films. The film containing 4.7 % Al prepared by target power of 800 W exhibited a high hardness about 16.5 GPa, a low internal stress about 0.62 GPa, a low friction coefficient about 0.055 and a low wear rate about 2.9×10-16 m3/(N?m) in the ambient atmosphere.