Abstract: As the speed of a vehicle on the highway can reach as high as over 100km an hour, so drivers on highways have less reaction time than drivers in other road situations. That’s why chain collision happens frequently on highways. In this paper, V2V (vehicle to vehicle) network is applied to solve the problem of chain collision on highways. Currently, the V2V network relies on periodic broadcast to disseminate the emergency warning messages (EWM) to locations beyond the transmission range of individual nodes on highways. But along with it, there comes the problem of broadcast redundancy, which reduces the reliability and efficiency of the warning system. In this paper, by studying different broadcast strategies, a new efficient IEEE 802.11 based broadcast protocol of communication in vehicle group is proposed for preventing chain collision on highways. The proposed protocol designs to figure out broadcast redundancy, transmission latency, reliability problems of multi-hop broadcast on highways, and achieves the purpose by sending the ACK frame to choose broadcast vehicles on the basis of directive broadcast. The simulation result shows that it can effectively handle the broadcast redundancy problem of EWM and achieve higher reliability but lower transmission latency of message dissemination among vehicles on highways.