The present invention relates to a transparent thermoplastic resin composition which characteristically contains A) 20-80 weight % of graft copolymer composed of a) conjugated diene rubber latex; b) intermediate layer prepared by copolymerization of acrylic acid alkylester derivative and aromatic vinyl derivative with the above a); and c) graft layer prepared by copolymerization of methacrylic acid alkylester derivative or acrylic acid alkylester derivative, a romatic vinyl derivative and vinyl cyan derivative with the above b) and B) 20-80 weight % of MSAN copolymer prepared by copolymerization of methacrylic acid alkylester derivative or acrylic acid alkylester derivative, aromatic vinyl derivative and vinyl cyan derivative. The transparent thermoplastic resin composition of the present invention has enhanced transparency, impact strength, surface gloss, weather resistance and color by being prepared by the method of the invention which is characterized by the steps of forming an intermediate layer by adding acrylic rubber to polybutadiene rubber, grafting, and regulating refractive indices of each monomers of a copolymer.