In order to improve the efficiency of message transmission in intermittently connected mobile networks, an Adaptive Routing Protocol Based on OLSR (ARPBO) of mobile ad hoc network is proposed. ARPBO forwards messages rapidly by the OLSR protocol when the network is connected. When the network is interrupted, ARPBO extends the OLSR protocol, selects the next hop node effectively by the message transmission node's local connected network, and then forwards messages through the "store-carry-forward" mechanism of delay tolerant network. The experimental results show that the proposed routing protocol can achieve higher message delivery success ratio and lower delivery delay when the network is intermittently connected.