Abstract: Polyimide (PI)/Molybdenum disulfide (MoS_2) intercalation composite was prepared way of polymerization of the intercalated monomers. The resulting composite was characterized by means of powder X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy, using raw material MoS_2 as a reference. The effect of the PI/MoS_2 intercalation composite as an additive on the tribological properties of commercial lithium grease was examined using a four-ball machine. The worn steel surface was analyzed by means of scanning electron microscopy and X-ray photoelectron spectroscopy. As the results, the PI/MoS_2 intercalation composite as the additive in lithium grease at proper concentrations was effective in improving the antiwear and friction-reducing behavior of the lithium grease. This was attributed to the formation of a surface protective film composed of FeSO_4, MoO_3 and iron oxides on the worn steel surface.