Wireless Ad-hoc networks, is mainly applied to build a small home local area wireless network. The main features are as follows: network autonomy, dynamic topology, changes in bandwidth limitations and link capacity, multi-hop communication, distributed control, limited security. Typically, the mobile wireless network thanks to a radio channel, limited power, distributed control and other reasons, will be more vulnerable to security threats than wired networks. The paper proposed a multi-channel three-demission probability CSMA protocol based on three-way handshake mechanism for wireless Ad-hoc networks. By introduction of the inquire response mechanism increases the reliability and stability of the system, reducing the collision possibility of the information packets to a certain extent, improves the channel utilization; by the use of the multi-channel mechanism, not only enables the channel load balancing, but also solves the problem of the hidden terminal and exposed terminal. Therefore, such system ensures the safety and reliability of the communication system to reduce the collision probability and increase the throughput. The computer simulations show that choices of three-demission probability have a great influence on the system throughput, make the system meet the different priorities with different QoS both efficiently fairly.