Abstract: The friction coefficent(μ)-time(t) transients of anodic film on 7070 Al Alloy were measured in the process of the film being worn by a small steel ball. It was found that the friction coefficent tended to increase during wearing. A phenomenon of periodic change of the friction coefficent, which increased steply and then changed slowly, occured repeatly. The friction coe-ffient were related not only to the abrasion of the sample surface but also to the fibre-boundies cracking in the subsurface layer of the anodic film.