Medium Access Control(MAC) protocol has a great impact on the performance of wireless networks, and it has become a key factor to achieve efficient wireless communications．The Wireless Local Area Network(WLAN) and channel access scheme are firstly introduced, then the research of multi-channel MAC protocol is performed. A typical multi-channel MAC protocol based on common control channel is presented, which is denoted as Dynamic Channel Assignment(DCA) protocol. In order to improve the channel resource utilization of DCA protocol, a multi-channel MAC protocol based on Transmission Opportunity(TXOP) transmission mechanism is proposed, namely T-DCA，i.e.，TXOP based DCA. Because the T-DCA protocol is simple for implementation, it can be utilized in distributed wireless networks, such as Ad-Hoc and WLANs. Finally，the superiority of T-DCA protocol is evaluated by extensive simulations that are deployed using NS-2 simulator. The simulation results show that the T-DCA protocol can not only effectively deduce the collision probability，but also improve the network throughput and reduce the average packet delay.