A polymer-chain-grafted carbon nanocapsule. The polymer-chain-grafted carbon nanocapsule includes a carbon nanocapsule and at least one kind of polymer chain grafted thereon, forming a polymer-chain-grafted carbon nanocapsule in which the carbon nanocapsule is the core thereof. The polymer-chain-grafted carbon nanocapsules have the following formula: F(-P)m, in which F is the carbon nanocapsule, P is the polymer chain, and m is the number of the polymer chain. By grafting high-purity carbon nanocapsules with polymer chains, the application thereof is expanded.