Abstract: To solve the high backbone network pressure, long startup delay and high frame loss rate of the random P2 P streaming system, a neighbors' selection algorithm based on round-trip time (RTT) and bitmap was proposed. The algorithm used the Tracker to store the round-trip delay between nodes and the Buffer-Map bitmap across the network, and the node sent a request to the Tracker, then the Tracker sent the best neighbor list based on the node's RTT information, bitmap information and the screening function to the node. The simulation result shows that the algorithm effectively reduces the node startup delay, playback delay and frame loss rate compared with a random neighbors' selection algorithm.