Abstract: Inorganic borates are a new kind of effective antiwear and extreme-pressure oil additive without harmful effect. Many works have been done to develop the inorganic borate oil additive in the last decade. In this paper, the molecular structrue, the preparation and the antiwear mechanism of borates additives were described. Inorganic borate additives are non-hazardous, free of smell, have good antiwear ability and high load-carrying capacity. With the combination of inorganic borate additive with succinimide dispersant, the antiwear ability can be improved, whereas with sulfonate dispersant, the antiwear ability decreases. Tests have shown that an inorganic borate protective surface film is formed on the rubbing surface to possess antiwear and extreme-pressure properties. It is pointed out that more work should be done to study the tribological properties of the blends of inorganic borates and S,P and C1 containing additives, and to improve the stability of borate oil.