In this paper, a new MAC protocol supporting cooperative diversity named as CD-Maca is presented. By making use of the information carried by the handshaking frames of the Maca protocol, which has been employed in IEEE 802.11 standard, the CD-Maca protocol allows terminals in the network to transmit data frames cooperatively, resulting in more reliable retransmission and better performance. We model the CD-Maca protocol with Markov chain and derive the throughout of the protocols. It's shown by numerical results and simulations that the performance of the CD-Maca protocol depends on the packet error ratio (PER) of the handshaking frames, the PER of the cooperative transmission and the network topologies.