The invention discloses a multichannel diversity-based cognitive medium access control realizing method, which is designed on the basis of multichannel diversity. In the method, source nodes and target nodes compete for the right of use of a data channel through exchange control packets on a public control channel, node pairs wining the competition determine data channels and corresponding power allocation for the transmission according to power/channel combined allocation and are shifted to corresponding data channels to transmit a plurality of data packets continuously. The invention also provides a method for resolving power/channel combined allocation, which is to resolve the power/channel combined allocation by converting the power/channel combined allocation into a multi-choice knapsack problem and by dynamic planning. Simulation results show that the cognitive MAC protocol can effectively improve intra-node pair data transmission rate and network throughput under a condition that the total transmission power is limited compared with an opportunistic multiradio MAC (OMMAC) protocol.