Abstract: A ferrofluid with extremely low evaporation, moderate viscosity, and good lubricity was used to replace the grease for the lubrication of a roll bearing. Thus the lubrication and seal of the roll bearing based on the ferrofluid was realized, by making use of the rotary sealing of the ferrofluid with zero leakage and extremely small wear debris generation and replacing the conventional rubber seal with the combined rotary seal of the radial magnet and the ferrofluid. The ferrofluid lubricating and sealing performances of the roll bearing was investigated. It was found that the developed roll bearing had little lubricant evaporation loss and wear debris generation as well, and it could find promising application in extremely clean environment.