Abstract: With the manner of storing-carrying-forwarding, nodes can communicate with each other in opportunistic network, but the limited buffer should be used reasonably. Based on message redundancy estimating, an adaptive buffer management mechanism is proposed in this paper. According to the nodes activity degree and the number of message copies, the status of message transmitting in the network can be predicted; moreover, with the parameter of message redundancy, the decision on message receiving and forwarding can be made dynamically. Numerical results show that the methods to evaluate nodes activity degree and number of message copies are accurate; furthermore, comparing with other buffer management mechanisms, the proposed mechanism can improve message delivery rate effectively, reduce latency and overhead ratio.