Ba0.7Sr0.3TiO3 nanoparticles were successfully synthesized by mechanical alloying and successive ultrasonic irradiation method with an addition of surfactant. Fine crystalline particles were first obtained after re-milled the sintered mechanically alloyed powders of BaCO3, TiO2 and SrCO3 precursors for 20 hours in which the size of particles was found below 300 nm. These fine particles were further refined their size under a high power ultrasonic treatment for 6 hours. Various types of surfactant namely amphoteric, cationic, anionic and non-ionic were brought into studies to find out their effectiveness in preventing the agglomeration due to strong attractive forces between fine particles. It was found that all surfactant prove effective to prevent the agglomeration. This was indicated in the distribution of particle size measurement in which mean size of particles added surfactants (139 nm-158 nm) was less than that of surfactant free (173 nm). However, among all surfactant which added in the media containing particles, only the non-ionic surfactant showed a particle size distribution with the smallest (139 nm) mean particle size. The effectiveness of surfactant in preventing the agglomeration depends on the concentration of surfactant and density of media containing particles. The study concluded that the addition of 0.1% non-ionic surfactant into media containing particles has resulted in Ba0.7Sr0.3TiO3 nanoparticles with the mean size of 139 nm.