Abstract: This paper analyzes the existing P2P soft wares and their deficiency and inability to transmit data efficiently and hereby presents a new kind of P2P file transmission system architecture. This architecture is based on the existent IPv4 network,working on a unique three leveled multistage RootServer-GroupServer-User structure to improve efficiency. UDP-tunnel technology is employed to solve the problem in realizing the NAT-NAT data transmission. A new search-mode is adopted, files are well classified and indexed, and all of the processes of file transferring are properly monitored in this architecture. The results of the running of the system prove that the system makes an efficient use of the network bandwidth and the efficiency of file transmission is highly increased.