The present invention relates to a method of preparing rubber-modified styrene copolymer resin with excellent transparency and impact resistance, specifically to a method of preparing transparent resin of rubber-modified styrene copolymer comprising graft-copolymerizing styrene monomer and (meth)acrylate monomer in the presence of block or random styrene-butadiene copolymer which has 30-50% of styrene skeleton content and 20-40 cp of 5% toluene solution viscosity at 25 iÉ. According to the method of the present invention, the transparent resin containing the rubber particles of a double structure comprising onion and core-shell structure can provide transparent resin of rubber-modified styrene copolymer resin with excellent transparency and impact resistance as well as good gloss.