The network collaboration system refers to that the users in different locations can see and hear each other through the collaboration system, and can share and browse the text, video, web pages, etc., so as to achieve the purpose of joint work and joint learning. Based on the needs of this collaboration system, this system was studied and designed, the system was based on P2P bottom layer and designed different logical topologies under different collaborative application circumstances, and it designed the topology with the combination of mesh and tree structures according to the particularity of P2P live broadcast, moreover, regarding keys affecting the system performance, i.e. service node lookup, it proposed new algorithm and conducted the optimization.