The buffer resource utilization in opportunistic networks can be improved by efficient buffer management strategy. The delivery probability of message is directly related to its necessity of forwarding and buffering. An adaptive buffer management strategy with message delivery probability estimating method is proposed. Through establishing the node connection status analysis model, the diversity of node service ability could be evaluated. Accordingly, to estimate the delivery probability of the message. Furthermore, the transmitting and removing priority could be determined reasonably to perform buffer management operations. Numerical results show that overhead ratio can be reduced about 57% by the proposed buffer management strategy. The delivery ratio is improved and the delivery latency is reduced efficiently.