Abstract: In order to solve the reader collision problem in radio-frequency identification (RFID) networks, a collision avoidance asynchronous multi-channel medium access control (MAC) protocol is proposed. Each reader monitors the control channel, thus obtains the occupied channels and communication states of neighbor readers. Then, an unused channel is adaptively selected as the communication channel to transmit request to send (RTS) to its neighbor readers to broadcast this choice. Thus the non-collision communication is realized. To avoid the reader to tag interference, neighboring readers are forbidden to communicate with the same tag simultaneously. Therefore, the reader frequency interference can be avoided by adopting the multiple-channel communication mechanism as well as space-division multiplexing frequency.