The design and evaluation of accelerated transmission (AT) systems in peer-to-peer networks for data transmission are introduced. Based on transfer control protocol (TCP) and peer-to-peer (P2P) substrate networks, AT can select peers of high performance quality, monitor the transfer status of each peer, dynamically adjust the transmission velocity and react to connection degradation with high accuracy and low overhead. The system performance is evaluated by simulations, and the interrelationship between network flow, bandwidth utilities and network throughput is analyzed. Owing to the collaborative operation of neighboring peers, AT accelerates the process of data transmission and the collective network performance is much more satisfactory.