Graft-copolymerization of vinyl monomer containing silica precursor, p-styryltrimethoxysilane, onto natural rubber microparticles was performed in latex stage to form three-dimensional networks of nanosilica. After the latex was cast into a film, morphology observation by transmission electron microscopy showed that the natural rubber microparticles were dispersed in organic-inorganic nano-matrix consisting of vinyl polymer and silica nanoparticles. In particular, generation of large silica particles was prevented by slow rate of hydrolysis and condensation of silicon alkoxides for p-styryltrimethoxysilane and the nanosilica networks were formed. The nanomatrix structure with the nanosilica networks increased tensile strength of the rubber, and destruction of the structure decreased the strength. Master curves of dynamic moduli of the rubber showed that the value of storage modulus at rubbery plateau region was high and it was almost flat at low-frequency region because of the nanosilica networks. (C) 2016 Elsevier Ltd. All rights reserved.