Abstract: The problem of optimal sensor set (OptSS) selection in cognitive radio networks is considered in this paper. Although the method of cooperative spectrum sensing can greatly improve the sensing performance， the consumption of system resources will increase as the number of cooperative sensors increases， therefore， the number of cooperative sensors to use is a compromise between sensing performance and consumption of system resources. To the best of our knowledge， this is the first effort to select OptSS for cooperative spectrum sensing in cognitive radio， under sensing performance requirements. Based on the expression for the probability of detection which is characterized as a function of the number of cooperative sensors and the global average receiving signal to noise ratio of OptSS， an optimal sensor set selecting algorithm is proposed. Simulation results demonstrate the effectiveness and reliability of the proposed algorithm.