Abstract: In cooperative communication, the relay node is used to retransmit the data packets of the source. However, helping other nodes transmitting packets may decrease the performance of the relay, it is less efficient from the point of the relay, which is called the relay inefficient problem in cooperative communication. In order to resolve this problem, a cooperative MAC is proposed based on network coding for Ad hoc networks. The proposed protocol combines the network coding and cooperative communication and allows a relay to use the cooperative retransmission to deliver its own data packets as well. Such a special scheme resolves the relay inefficient problem by network coding and improves the system performance as well. Moreover, the proposed protocol is modeled by a modified Markov chain in the multihop networks, in which considers the cooperative communications and the network coding. Furthermore, the impacts of multihop and channel condition for the system performance are also discussed in this paper. The simulation results show the proposed protocol can significantly improve the system performance compared with the general cooperative MAC and the network coding is really efficiency to resolve the relay inefficient problem in cooperative communication.