The present invention relates to an organic-inorganic nanocomposite and preparation thereof and particularly to a method for preparing an organic-inorganic nanocomposite capable of uniformly dispersing a silicate compound in a polymer medium by adding monomers, an initiator, and an emulsifier to an ion-exchanged layered silicate salt that is prepared by adding a cationic initiator and a cationic chain transfer agent to a layered silicate compound to cause polymerization.