A novel cluster expanding and scheduling strategy is put forward，and then a multi-channel medium access control (MAC) protocol is designed for wireless sensor network (WSN) applications that ask for high network throughput and low transmission delay. The proposed MAC protocol based on TDMA can effectively improve throughout and channel utilization with a controllable hybrid channel access method. The protocol is simulated with OMnet++ software and the outcomes show that the protocol has good throughput performance and low delay time.