ABSTRACT This paper analyzes the security performance of underlay cognitive energy-harvesting relay radio networks (UCEHRRN) through the Monter-Carlo simulation results. The results clarify the influence of critical operating parameters on the security performance of the system. Furthermore, the security capabilities of UCEHRRN have been compared with those of the live transmission system. Moreover, many results show that the security performance of the system is significantly improved. Analysis of the results also shows that UCEHRRN is especially effective when the direct transmission system cannot achieve security due to objective reasons such as path loss, severe fading, and shadowing.