Peer-to-Peer (P2P) architectures let participants gather resources form network and make participants acquire more computation resources than they could offer. One of the most prominent P2P systems is P2P file sharing system. P2P file sharing system could be classified into to 2 categories: centralized and decentralized model. BitTorrent-like model is a kind of decentralized and unstructured model. BT-like model is quit popular nowadays due to its scalability. Unfortunately, BitTorrent-like model has several shortcomings on performance over asymmetric networks, because of these problems: fractional upward bandwidth, blockage of acknowledgement and long physical paths. There are no complete solutions for blockage of ackownlegement. We propose a new UDP-based protocol to alleviate this problem. UDP protocol lacks for data-integraty and can’t determine transmission rate by its own. To form a complete solution, we have to design some co-operating mechanisms for UDP, such as packet loss recovery, segment size determination and data rate determination mechanism etc. Experiments have shown that our proposed protocol has good improvement on performance. We hope that our protocol would help P2P file sharing participants have performance gain.