This paper focuses on the second-order statistics analysis for a cooperative cognitive radio network with Nth best relay (CCRN-NthR) based on reactive decode-and-forward (RDF) protocol. The second-order statistics include average outage rate (AOR) and average outage duration (AOD). To these ends, we first obtain the exact closed-form expressions for the AOR and AOD of the equivalent end-to-end SIR. Then, based on the derivations, the simulations are presented. The simulations show that the derived theoretical analysis results are agreed with the simulations. At the same time, in the simulation selection we investigate the impact of system parameter N. It is obtained that in high Q only the value of N affects the diversity gain. The AOR benefits from an increased diversity gain, but the AOD does not.