Abstract: Five carboxylic lead salts, namely, lead laurate (LL), lead oleate (LO), lead naphthenate (LN), lead stearate (LS) and lead alkylsalicylate (LAS) were synthesized by in situ fusion process, precipitation process, and microwave assisted method in 200SN base oil. Their tribological properties as friction reducing, anti wear and extreme pressure additives for lubricating oil were evaluated with a four ball machine. The action mechanisms of the additives were discussed as well. The results indicate that the oil solubility, anti wear and friction reducing ability, and extreme pressure load carrying capacity of the compounds as additives are dependent on the molecular structure. LL and LAS exhibit the best oil solubility, LL possesses the best anti wear and extreme pressure properties, while LO shows the best friction reducing ability. The difference in the alkyl group of the organic lead salts accounts for the difference of their adsorption on the frictional pair surface and hence the strength of the boundary lubricating film as well. This leads to the difference in the chemical composition and physical properties of the boundary lubricating film and thus the tribological behavior as well. Namely, the alkyl groups with stronger absorption ability usually give better tribological behavior. The formation of PbO in the boundary lubricating film contributes to improve the wear resistant ability and load carrying capacity.