Ad hoc networks are envisioned to have dynamic, sometimes rapidly-changing, random, multihop topologies which are likely composed of relatively bandwidth-constrained wireless links. The dynamic source routing protocol (DSR) is a simple and efficient routing protocol designed specifically for use in multi-hop wireless ad hoc networks of mobile nodes, however, due to mobility and line broken, the route information stored in the cache will be easily invalidated. In order to solve the problem, this paper introduces a new mechanism to optimize the process of route request in DSR router protocol. Two metrics were used to evaluate the performance: sent/received traffic and end-to-end delay, respectively. And two scenarios were analyzed showing the improvement of the network performance with respect to the original DSR protocol.