Abstract—Due to the fact that security and energy efficiency are investigated separately in the conventional Primary User Emulation Attack (PUEA) countermeasure strategy in Cooperative Spectrum Sensing (CSS) process, the tradeoff between security and energy efficiency is discussed in this paper. CSS can improve detection performance whereas energy consumption will dramatically boost up with the increasing of cooperative users. To tackle this problem, we set CSS energy efficiency in the presence of PUEA as optimal objective, whereas secure detection performance and secure false alarm threshold as the constraint conditions. The optimal problem is resolved to achieve a trade-off between energy efficiency and security in the presence of PUEA attack. The optimal fusion threshold K and optimal cooperative user numbers can be obtained in secure CSS with energy efficiency maximization, which guarantees energy efficiency as well as secure CSS detection performance. The proposed PUEA countermeasure strategy detection performance is presented and compared with traditional Maximum Ratio Combining (MRC) fusion rule. Simulation results show that, the proposed strategy is immune to PUE interference power, and it provides high robustness to PUEA attack, which implements the trade-off between security and energy efficiency in Cognitive Radio Network (CRN) effectively.