Abstract: A series of multiply-alkylated cyclopentanes (MACs) were synthesized. In comparision with perfluoropolyether (PFPE), these compounds as promising lubricants for steel/steel contact were evaluated by an SRV test rig in a ball-on-disc configuration. It is found that multiply-alkylated cyclopentanes had better antiwear ability than that of perfluoropolyether. The correlation between the chemical structure of the compounds and their friction-reducing and antiwear behaviors was discussed. An action mechanism of the lubricants was proposed, based on the observation and analysis of the morphologies of the worn steel surfaces with a scanning electron microscope, the analysis of the chemical states of the worn surfaces on an X-ray photoelectron spectroscope, and the datas of gel permeation chromatograph (GPC). In the beginning, boundary lubricating film of MACs was formed on the steel worn surface by physical adsorption, this contributed to reduced friction and wear. The generation of a boundary lubricating film containing Fe₂O₃ and polymer reduced friction and wear, while the reaction of MACs with the steel surface occurred at elevated temperature.