Abstract: Nano-silica/epoxy resin composites were prepared by dispersion technologies as ultrasonic disperation,mechanical agitation and surface treatment of nano-silica particles. The microstructures,tensile mechanical properties,dynamic mechanical properties and hydroacoustic performance were studied by scanning electron microscopy(SEM),universal testing machine,viscoelastometer and acoustic impulse tube test system,respectively. The results indicated that,nano-silica were uniformly dispersed on nano scale in the epoxy with the ultrasonic dispersion method and the pretreatment method. Compared with pure Epoxy. The tensile strength and the elongation at break of nano-silica/epoxy composites were increased by 5%-30% and 2%-14% respectively,compared with those of the pure expoxy. With improved dispersion of nano-silica,the storage modulus of nano-silica/epoxy composites was improved,while the loss factor decreased. The sound absorption performance of the nano-silica/epoxy composites was 6-10 times higher than that of the pure epoxy. The finer the nano-silica was,the more even the dispersion was. The homogeneous dispersion of nano-silica in epoxy had a positive influence on the tensile mechanical properties,dynamic mechanical properties and hydroacoustic performance of the nano-silica/epoxy composites.