A cognitive radio ad hoc network (CRAHN) can be considered as a special delay tolerant network (DTN) that is composed of mobile secondary users (SUs) with social characteristics. Given intermittent connectivity and spectrum availability, it is a challenging issue regarding how to transmit messages between SUs in a reliable and effective way in CRAHNs. To tackle this challenge, we propose a social-aware opportunistic routing and relay selection scheme, called SoRoute, which first predicts the link reliability based on a new social-relationship-aware mobility model and then fuses the relationships of SUs to make a routing and relay decision. In our design, different prediction schemes are employed for the nodes with different relationships. A message is forwarded to the relay node with the largest encounter probability with the destination. The evaluation results demonstrate that our social-based opportunistic routing scheme significantly improves the performance compared to the existing routing schemes such as Direct Delivery, First Contact, MaxProp, and Prophet.