Abstract: Considering the challenges of information timeliness and data freshness to various real-time status update systems， an unmanned aerial vehicle （UAV） relay-assisted cognitive radio network （CRN） age of information （AoI） minimization scheme is proposed. To reduce the AoI at the secondary user receiver in CRN， UAV is used as mobile relay to assist the secondary user transmitter to transmit data packets to the corresponding receiver without affecting the normal communication of the primary user. The flight trajectory and resource allocation of UAV are jointly optimized to ensure the freshness of information. Since the joint design problem is nonconvex， an efficient iterative algorithm of successive convex approximation is used to obtain the optimal solution of the problem. Simulation results show that the proposed scheme can effectively improve the information freshness and obtain the minimum value of peak AoI. Meanwhile， the size and number of packets are linearly related to AoI and have an impact on the flight trajectory of UAV.