Abstract: TiN coating and TiN coatings doped with 10% and 20% (atom fraction) copper were prepared on copper substrate by multi arc ion plating. Using 1-octyl-3-methylimidazole double (trifluoromethane sulfonyl) imide salt (OMImNTf₂) and 1-dodecyl-3-methylimidazole double (trifluoromethane sulfonyl) imide salt (C₁₂MImNTf₂) as the lubricant, the effect of coating and ionic liquid composite lubrication system on current-carrying tribological properties of copper/copper friction pair at different voltages (0.5,1 V) were studied. The results show that the TiN coating/OMImNTf₂ composite lubrication system showed relatively good synergistic lubrication effect at the same voltage, while the TiN coating/C₁₂MImNTf₂ composite lubrication system exhibited relatively good conductivity property. The difference of friction coefficient and contact resistance of friction pair under composite lubrication system of copper-doped TiN coating and two ionic liquids was very small. When the voltage increased from 0.5 V to 1 V, the tribological properties of friction pair under composite lubrication system consisted of TiN coating,TiN coating doped with 10% copper and C₁₂MImNTf₂ was more stable. The friction pair containing TiN coating doped with 12% copper had the smallest friction coefficient and contact resistance.