Abstract: The molecular orbital parameters of two lubricating additives and iron atom cluster were calculated by using a quantum chemistry method. The interaction pattern between the additive and metal atom cluster was discussed based on the approximate rule of orbital energy. Some parameters characterizing the action strength between the additive and metal, including the bonding strength, reactive strength and static action strength, were analyzed by using frontier electron density, super de localizability and net atomic charge as criteria. The results show that the interaction between the additive 3 (N,N dibutyl dithiocarbamate yl) malonic acid and iron atom cluster is stronger than that between 3 (N,N dibutyl dithiocarbamate yl) propionic acid and iron atom cluster, and the prediction results based on quantum chemistry calculations are in good accordance with the friction and wear test results. Thus the quantum chemistry calculation can be used to guide the design of the lubricating additives.