Abstract: Ultrasound was introduced to prepare nano-Ga/PBA core-shell composite particles through emulsion polymerization.The microstructures were characterized by TEM.The effect of content of metal particle on composite emulsion polymerization was researched.The results indicated that nanoparticales are encapsulated by polymer.The composite nonaparticles formed are spherical and elliptical,they have core-shell structure with size of about 70-130 nm.The effect of content of metal particle on composite emulsion polymerization is complicated.