WSN which is a very important emerging technology in the information age, has caused great concerning all over the world, compared with current Wireless LAN, Mobile Communications Networks, Cellular Communications, Wireless Sensor Network has much more development potential. IEEE802.11 provides the following solutions. The use of RTS / CTS protocol, and set the upper limit of the number of bytes transferred, ensuring the plurality of mutually invisible transmitting station at the same time send a signal to the same receiving site. This paper presents the discrete time three-dimensional probability CSMA protocol with three-way handshake mechanism, and uses the average cycle analysis methods system throughput. The correctness of the theory is verified through the simulation.