In the cognitive radio network, to be directed against the primary user emulation attack(PUEA), in this paper, an improved energy detection algorithm is used in cooperative spectrum sensing(CSS) technology to improve the systematic performance. Supposing that the PUEA initiated with a certain possibility, in CSS technology and under the “hard” decision, we make improvement based on the traditional energy detection method that determine the threshold value by adjusting the related parameters and applying the Neyman-Pearson criterion, which effectively resist the malicious primary user emulation attack. The simulation results show that the systematic performance of the improved energy detection method is better than the traditional energy detection method in the presence of PUEA.