Abstract: Cu3Sn nanoparticles were prepared with ease by allowing bulk tin to react with copper acetate under ultrasonic irradiation. The microstructure and thermal stability of resultant Cu3Sn nanoparticles were analyzed by means of transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). In the meantime, the possible growing mechanism of Cu3Sn nanoparticles was presented; and the tribological properties of Cu3Sn nanoparticles as lubricating additives were evaluated. It has been found that as-synthesized hexagonal Cu3Sn nanoparticles are of spherical shape and have a narrow size distribution and an average diameter of 90nm. The growth of Cu3Sn nanoparticles involves three stages of ultrasonic dispersion, reaction and surface modification. Besides, ultrasonic irradiation in combination with surface-capping by oleic acid contributes to prevent on-growing Cu3Sn nanoparticles from aggregation, making it feasible for Cu3Sn nanoparticles to be well dispersed in lubricating base stock and significantly increase the antiwear ability and load-carrying capacity of liquid paraffin. [Copyright &y& Elsevier]