The technique of relative optical interference intensity (ROII) was used to investigate the effect of molecular ordered degree of cholesterol esters in hexadecane on lubricating properties in thin film lubrication (TFL) regime. The results indicate that transition from TFL to elastohydrodynamic lubrication (EHL) occurs when the rolling speed varies in the range from 30 to 70mm/s for pure hexadecane. However, when cholesterol liquid crystal (LC) was added into hexadecane, the tran-sition phenomenon disappears. The film thickness is closely related to the number of carbon atoms in LC alkyl chain, the LC polarity, the concentra-tion of LC in hexadecane liquid, and the applied external DC voltage. When the thickness of these lubricant films increases to about 30 nm, it nearly keeps constant and hardly changes with the volt-age. The formation mechanism of the thin lubri-cating film in the nano scale is discussed.