Multimedia streaming application is increasingly popular. P2P mode makes it much more suitable for large-scale users to participate into one single application. However, most effort is spent on issues such as overlay construction and content delivery. As a foundational aspect in P2P-based multimedia systems, buffer management needs more exploration and traditional measures should be refined. In this paper, a bandwidth adaptive buffer exchange strategy is proposed, which is similar to the slow start process in TCP protocol. A novel algorithm is applied in a live media streaming system, called Anysee, and has been proven resilient to the bandwidth fluctuation in P2P networks.