The cognitive radio technology is a new method for solving the problem how to improve theefficiency of radio resources. The OFDM technology is one kind of high speed multi-carrier transmissiontechnology under wireless environment. This article puts forward a policy of frequency selection and powercontrol in cognitive radio system based on OFDM technology. This method takes into account both the systemthroughput and the fairness；it can also change the parameters to adjust the algorithm complexity. At last thisarticle simulates the proposed algorithm. Simulation results show that the proposed algorithm can use thespectrum resources sufficiently by low implementation flexibility as well as meeting the requirement ofcommunication.