The present invention relates to a thermoplastic resin composition and a preparation method of the same, more precisely, a thermoplastic resin composition containing acrylate-styrene-acrylonitrile (ASA) graft copolymer resin, aromatic polycarbonate resin, aromatic vinyl compound and vinyl cyan compound copolymer resin and styrene-acrylonitrile graft maleic anhydride (SAN-g-MAN) to improve exterior physical properties such as scratch resistance, surface gloss, colorability, weather resistance, etc, and a preparation method of the same.