The impact of thickness of diamond-like carbon (DLC) coating on friction and wear performance was studied under sliding-rolling contact condition. The friction coefficient of coated roller was around 0.1 under non-lubrication in high-vacuum and 0.05 under oil lubrication. Wear occurred at the interface between the DLC coating and the matrix. The wear performance increased with increasing thickness of DLC coating. The radical nitriding pretreatment was effective against wear of the DLC coating. This is an abstract of a paper presented at the Proceedings of World Tribology Congress (Kyoto, Japan 9/6-11/2009).