Limitations of current multi-channel MAC protocols include requiring of strict time synchronization, existing large number of multi-channel hidden terminals, and lacking single-hop broadcast support and sleep mechanism, i.e. duty cycling. This paper proposes an asynchronous duty cycle based multichannel MAC protocol, called DCM, for wireless sensor networks. Instead of requiring time synchronization among nodes, DCM takes advantage of receiver-initiated cross channel handshake mechanism to make a channel reservation for data transmission, and employs receiver adjustment mechanism to tackle the problem of the loss of broadcasting data and to improve broadcast reliability. According to theoretical analysis using Queueing theory, this paper obtains the average number of available channels. The simulation and testbed experimental results show that DCM reduces the number of multi-channel hidden terminals effectively, and achieves significant improvement in network throughput with increasing benefit as traffic loads increase while maintaining higher energy efficiency.