Abstract: Based on the characteristic of vehicle mobile ad hoc network，for the first time，this paper analyzes the unstable situations of routing in vehicular mobile ad hoc network from the point of routing fracture，then proposes a GPS-free routing protocol RSBA（Relative Stability Based AODV Routing Protocol），with vehicle’s relative stability as it’s auxiliary parameter in routing establish process.Simulation shows RSBA’s lower route broken rate and routing overhead，as well as it’s better performances in reducing packet drop rate compared with AODV in high node’s density urban vehicle environment and validates the correctness of the analytic strategy and conclusions of the stability of vehicle mobile ad hoc network.