Surface modifiers with different lipophilic chain lengths, such as, lauric acid diethanolamine, myristic acid diethanolamine, palmitic acid diethanolamine and stearic acid diethanolamine, were used to prepare four kinds of LaF3 nanoparticles in the mixture solvent of water-ethanol. Morphology and surface modification of LaF3 nanoparticles were investigated by TEM, FTIR and TG. Effect of length of surface modifier lipophilic chain on tribological properties of LaF3 nanoparticles and their susceptibility to base oils were investigated by a four-ball machine. Results show that the tribological properties of LaF3 nanoparticles in the base oil in build up as lipophilic chain length of surface modifiers increases; the longer the lipophilic chain is, the better the susceptibility of the nanoparticles to liquid paraffin wax is. This is mainly because that the lipophilic chain length influences the interface activity of the nanoparticles, moreover, for homologous organic acid soaps, the longer the lipophilic chain is, the better its friction reducing performance is; the properties of base oils also influence the interface activity of the nanoparticles.