[Abstract] P2P (Peer-to-Peer) overlay network is one of the most popular distributed networks. It not only has advantages in scalability, but also can maximize the use of computing and storage resources of each terminal nodes. In the last ten years, P2P system is a hot topic in IT field. Recently, most researchers study structed P2P system, which is better than the former P2P structure. This paper focus on the routing algorithms based on DHT in second generation of P2P overlay networks.