Due to the utilization of location information, geographic ad hoc routing presents superiority in scalability compared with traditional topology-based routing in mobile ad hoc networks. However, the consequent solicitation for location presence incurs severe concerns of location privacy, which has not been properly studied. In this paper, we attempt to preserve location privacy based on the idea of dissociating user?s location information with its identity. We propose an anonymous geographic routing algorithm which includes three components to avoid the explicit exposure of identity and location in communication without compromising the efficiency guaranteed by geographic routing.