Diamond-like carbon (DLC) films demonstrated significant advantages in cutting and forming non-ferrous materials. The ultra-low friction coefficient and high surface hardness make DLC one of the most promising surface modification technologies available for processing advanced structural materials. In this study, Ti-doped and hydrogen-free DLC films (a-C:Ti) were synthesized by unbalanced magnetron sputtering of Ti and graphite targets. The high residual stress of the DLC thin films was dissipated through a compound interface ;consisting of a series of Ti, TiN, and TiCxNy graded interlayers. The target poisoning problem was resolved with a 2 kHz medium-frequency DC power supply. In addition, a 20-100 kHz variable frequency DC power supply was used for both are suppressing and substrate biasing. The effects of deposition parameters on film qualities were investigated by SEM/EDS, XRD, EELS and wear tests. Results demonstrated an improved DLC thin film with superior microhardness and adhesion strength compared with the conventional DLC deposited by PVD or PECVD processes.