Abstract: The friction and wear behavior of gray cast iron in sliding against Al 2O 3 ceramics under different conditions was investigated on an MM 200 friction and wear tester, with focus on revealing the friction reduction and wear resistant action of graphite in the gray cast iron under dry sliding and lubricating condition of distilled water, emulsion and a machinery oil. The morphologies of the worn surfaces were observed with a scanning electron microscope, while the elemental composition of the transferred layer on the worn surface of Al 2O 3 ceramics were examined by means of energy dispersive spectroscopy. As the results, the friction coefficient and wear volume loss of the frictional pairs are ranked as dry sliding > distilled water lubrication> emulsion or oil lubrication. The graphite in gray cast iron could function to reduce friction and wear effectively under dry sliding and water lubricated condition; while such friction reductionand wear resistant action of the graphite in the gray cast iron becomes indistinctive under the lubricating conditions of emulsion and a machinery oil.