Abstract: In order to solve problems due to cognitive OFDM system authorized user underutilized spectrum resources caused by the shortage of resources, the proposed optimal resource allocation strategy based on fish swarm algorithm. According to the principle of fair distribution ratio of sub-carriers, a reasonable allocation by AFSA cognitive power users, taking into account the cognitive users and authorized users without disturbing each other, taking into account the fitness function for judging the reasonableness of power allocation to achieve cognitive OFDM system capacity is maximized. Experimental results show that the algorithm in cognitive user interference to authorized users is less than the threshold requirements under the conditions, ensure the fairness of cognitive users subcarrier and power allocation, improve spectral efficiency, to achieve the maximum transmission rate of the system.