Considering practical application in cognitive radio system, a graph theory algorithm is applied firstly to rapidly allocate spectrums (channels), which provides distribution fairness, and then the game theory algorithm is used to optimize first distribution spectrums (channels) and complete spectrum redistribution between cognitive users. Finally, simulation results show that the spectrum resources can be fully utilized, and under power transmission constraints, each cognitive user optimizes its own utility (rate) and distributes reasonably power. The simulation verifies that joint algorithm based on graph theory algorithm and game theory algorithm is effective. 