The Research of Security of P2P Network File Sharing System Peer to peer network is highly huge, open and dynamic. The nodes in the network with autonomy, anonymity, can freely join in or leave the network, and they do not need to be responsible for their own behavior, which reduces the P2P file sharing system’s transaction success rate and brings a lot of serious hidden security danger. Some security issues in the P2P network file share system were studied in this paper. The reputation incentive mechanism is established to encourage nodes tocontribute own resources positively, increase network resources and promote the healthy development of network, which can improve the resources localization rate and transaction success rate to enhance the network’s security.