Cognitive radio possesses the ability of solving the low spectrum utilization problem, which is introduced to the next-generation cellular networks. And the security under imperfect conditions should not be neglected due to the broad cast and uncertain characteristics of the wireless channels. In cognitive radio systems, interference between primary users and secondary users greatly affects the system performance. Based on interference alignment technique, the mutual interference between the primary network and the second network is efficiently managed and utilized, and the optimal precoding/beamforming schemes are designed to enhance the physical layer security performance. Finally, Monte Carlo simulations validate and prove the feasibility of the application of interference alignment technique in the nextgeneration cellular networks under imperfect conditions.