Quite recently,with development of the nano-technology,nano-particles of metal,metal oxides and non-metal have been used in industrial application as additives in lubricating oils.In this condition,a protecting surface layer can be formed to compensate the wear loss because of physic-chemical interaction between nano-particles and metal substrates.In order to understand the formation mechanism of the frictionally-formed coating,a series of friction and wear experiments were carried out in AMSLER friction and wear tester under different normal loads using hydroxyl silicate magnesium particles as oil additive.