The current Internet architecture lacks flexibility. The new network services are always postponed by tedious standardization process. The active network makes change through adding computing to network node. In this paper, the background and the motivation of designing active network are described, the new architecture is presented in detail, its effect on network architecture is discussed, and the current researches about active network are summarized. Finally, combining with the conclusion of network dynamics, a novel application based on active network is put forward.