For the purpose of improving the Korean Decimal Classification (KDC) in the design field, this study investigated the classification systems of design research suggested in previous studies and compared KDC, DDC, LCC, and NDC. The problems identified from the current KDC include lack of subdivisions regarding basic design theories and major design application fields and the absence of notes for explaining the scope of each design field. To solve these problems, this study suggested improvements for design theories, graphic design, industrial design, and environmental design.