Abstract. Multiple hop transmission is widely utilized in Mobile Ad Hoc Networks, most of the relay nodes play as cooperators in transmitting to help packets delivery. However, in this paper, a novel MAC-layer protocol based on coordinating relay node is proposed and analyzed. The relay nodes act as coordinators instead of cooperators and can save the transmission time and decrease the collision efficiently. We also propose assistant nodes to assist relay nodes in multiple hop transmission, which can decrease queuing time and increase the transmitting diversity. In order to reduce collision in sending terminal and receiving terminal, each node in our protocol is equipped with two interfaces, one is for sending and the other is for receiving. System analysis and simulation results of the presented protocol are shown in this paper to show the significant advantages in the performance of our protocol.