Abstract: A routing protocol in ad hoc networks based on RSU is proposed. The protocol uses the tree topology structure and the road network is divided into several traffic control area (TCA) which used the wireless or wired mode to connect the control center. It made a traffic control center (TCC) as a root node and RSU as a routing node in each TCA and it constructs a dynamic network of RSUs by this protocol. The experimental simulation shows that, by using the dynamic network of RSUs，this protocol can realize communications of vehicle to road and vehicle to vehicle, and it can improve the information publishing and the data aggregation of VANETs greatly.