The environmentally friendly biomimetic lubrication system was designed by tethering poly electrolytes on the substrates with sufficiently high grafting density, so-called 'polymer brushes'. The hydrated brushes in aqueous media formed water lubrication layer to reduce friction coefficient, which is useful not only for artificial joints and bio-devices but also for various mechanical devices. Macroscopic tribological properties of polyelectrolyte brushes bearing ammonium salt, sulfonic acid, or phosphorylcholine unit were characterized by ball-on-plate type tribotester in the air, water, and salt solution through sliding a glass ball on the surface under a normal pressure of ca. 140MPa. The low friction coefficient below 0.02 was observed in polyelectrolyte brushes in water.