Directional Medium Access Control protocols (DMACs) have been studied for decades. Since most existing DMACs assume an ideal antenna model which does not consider the minor-lobe interference, their performance cannot be guaranteed in practice. Other approaches assuming non-ideal antenna require either extra equipment or clock synchronization, making the system more complicated. It is also observed that directional transmission is rarely discussed in multi-channel scenarios. In this paper, a Cooperative Multi-channel Directional Medium Access Control protocol (CMDMAC) is proposed, incorporating directional transmission and multi-channel transmission to enhance system performance. Without making the terminals more complex or requiring clock synchronization, CMDMAC uses cooperative methods to solve the hidden terminal and deafness problems, taking into account minor-lobe interference effects of the directional antennas. Protocol performance is studied via simulation in NS2, showing that CMDMAC has good performance in terms of throughput and data packet transmission ratio.