Ti-doped diamond-like carbon(Ti-DLC) coatings and undoped diamond-like carbon(DLC) coatings were synthesized by unbalanced magnetron sputtering using carburized Chromium Molybdenum Steels (SCM415) as substrates. Nanocomposite structure coatings with metal carbides nanocrystals uniformly dispersing in the amorphous carbon matrix were obtained by the optimization of the kinds of doped metals and deposited parameters. This kind of nanocomposite structure permits improved hardness while maintaining a lower residual stress and getting thick coatings. The friction coefficients of Ti doping DLC coatings are relatively lower compared with undoping DLC coatings in engine oil. The analysis on the wear surface of coatings have indicated that: the surface of DLC doped with metal absorbs more elements from the engine oil, which indicates that the doping of metal can improve the affinity of the coating for the engine oil, enhance the formation of lubrication oil films, and reduce the friction coefficient thereby.