Abstract: In this study, optical interferometry was adopted to measure grease EHL films to reveal the influence of thickener fiber structure. Experimental results show that because of its fine continuity grease with coarse fiber structure formed thicker sedimentary layer in the rolling track, and by using fresh grease the lubricating film thickness was 2 to 5 times higher than that by the fine fiber grease. In the test with up-down speed sweep, the film thickness of the coarse grease showed significant difference from that of the fine grease in the first circle of speed sweep. However, after several circles of up-down speed sweeps, film thickness vs speed curves for coarse fiber and fine fibers presented similar change.