Aiming at improving their tribological behaviors, adhesion of diamond-like carbon (DLC) films on high-speed steel was investigated by varying doping silver (Ag) contents in a mid-frequency dual-magnetron sputtering system. Scratch testing was performed on the Ag-DLC films under a progressive normal load from 3 to 80 N, along with a Rockwell C indenter at a relative displacement speed for a Rockwell testing. A microscopic analysis of the scratch evolution under a progressive normal load permits identification of the various traces and the damage mechanisms of the films. A process of the film adhesion failure typically in turn appears like this, germination of the cracks along the longitudinal edges of the scratch traces; propagation in front of the indenter; and, detachment in the subsurface by shearing. An Ag-DLC film of 15.2 at% Ag exhibits a superior adherence on the steel substrate as compared with the three Ag DLC films of the other doping silver contents.