Abstract: Aiming at single radio multi-channel MAC protocol’s problems, such as the requirement of time synchronization and lots of orthogonal channels, large number of multi-channel hidden terminals, loss of single-hop multi-channel broadcast data, etc, the authors propose a competition based multi-channel MAC protocol, called HM-MAC, to tackle those problems for wireless sensor network. In HM-MAC, all the nodes work without time synchronization, use few orthogonal channels and take advantage of handshake mechanism to reduce the number of multi-channel hidden terminals. Meanwhile, a probability based sender adjustment broadcast scheme is presented, which reduces the loss of data and improves broadcasting efficiency. By theoretical analysis of the unicast mode, the number of used channel as well as the number of multi-channel hidden terminals are obtained. And, via theoretical analysis of the broadcast mode, the broadcasting efficiency of HM-MAC broadcast scheme is also obtained. More importantly, broadcast efficiencies of current multi-channel broadcast scheme are analyzed theoretically. In addition, a detailed comparison between HM-MAC broadcast scheme and other multi-channel broadcast schemes is presented. Finally, the theoretical analysis is verified via simulation experiments. The results of simulation experiment show that HM-MAC reduces the number of multi-channel hidden terminals effectively, and improves broadcasting efficiency as well as network throughput significantly.