With the proliferation of high-end mobile devices that feature wireless interfaces, many promising applications are enabled in opportunistic networks. In contrary to traditional networks, opportunistic networks utilize the mobility of nodes to relay messages in a store-carry-forward paradigm. Thus, the relay process in opportunistic networks faces several practical challenges in terms of delay and delivery ratio. In this paper, we propose a novel P2P Query algorithm based on Betweenness Centrality Forwarding (PQBCF), for opportunistic networks. PQBCF adopts a forwarding metric called Betweenness Centrality (BC), which is borrowed from social networks, to quantify the active degree of nodes in the networks. In PQBCF, nodes with higher BC are preferable to serve as relays, leading to higher inquiry success ratio and lower inquiry delay. A comparison with the state-of-the-art algorithms reveals that PQBCF can provide better performance on both the query success ratio and query delay, and approaches the performance of Flooding with much less resource consumption.