A type of brush-shaped copolymer with natural DNA as the main chain is synthesized. Multiple alkyne groups are introduced onto the phosphate backbone of natural DNA via an O-H insertion reaction, thus rendering the DNA sequence reactive for the subsequent grafting with azide-terminated poly(ethylene glycol) (PEG-N-3) by click reaction. This is the first synthesis of natural DNA as a main chain brush-shaped copolymer. The resulting novel copolymer may have potential for electrochemical DNA biosensors and gene delivery.