Abstract: Cr doped DLC films were prepared on samples with different roughness by magnetron sputtering/plasma assisted vapor deposition. Effect of the substrate roughness on friction and wear properties of Cr doped DLC film under dry-sliding condition was studied. The results show that the Cr doped DLC film on sample with low surface roughness exhibited good self-lubrication properties. The average friction coefficient was below 0.1, which was comparable to that under oil-lubricating condition. Meantime, the mild wear and the film structure on worn surface was well preserved without significant graphitization. However, the average friction coefficient was raised by 3–4 times on samples with high surface roughness. The wear was severe and wear surface included obvious grooves and severe wear of the coupled Si₃N₄ ball.