Organic–inorganic composite microparticle having interior nanostructures is one of the promising materials for creating a novel class of functional materials. In this paper, we show a simple co-precipitation method for silica nanoparticles and polymer composite particles by mixing water with water dispersed silica nanoparticles into tetrahydrofran THF solution of amino-terminated poly (butadiene)(PB) and evaporation of THF. High loading of inorganic nanoparticles into polymer particles was achieved and this high loading of inorganic nanoparticles was also an advantage for creating highly porous polymer particles by removal of inorganic part with HF. Interior structures of composite particles can be controlled by phase-separation of polymers.