The present invention relates to a method for easily producing nanoparticles by expansion, explosion, vaporization, condensation and cooling of plasma in a liquid by means of heat resistance and, more particularly, to a method for preparing a silicon nanocomposite dispersion having a uniform carbon layer coated on the surface of silicon of which at least one area is connected to a silicon carbide formed by reacting a carbon in liquid (C) during expansion, explosion, vaporization, condensation and cooling, and applied products thereof.