Graft-copolymers for improving impact strength comprising a relatively large quantity of an elastomeric trunk polymer, such as acrylonitrile/styrene/butadiene resins and methyl methacrylate/styrene/butadiene resins, have some undesirable powder characteristics, for example, poor fluidity and an easily blocking property.However, by blending a graft-copolymer of this type with a graft-copolymer comprising a relatively small quantity of an elastomeric trunk polymer in slurry form or dry state, it is possible to obtain a graft-copolymer blend with improved powder characteristics without significantly lowering the effect of improving the impact strength of the former graft-copolymer.The graft-copolymer blend thus obtained, when blended with a hard resin such as polyvinyl chloride, provides a resin composition with high impact strength.