Considering the limited energy of IoT devices, this study investigates a wireless powered communication network (WPCN) assisted by an intelligent reflecting surface (IRS) and interfered by a jammmer whose location information is incomplete. Our goal is to maximize the average throughput of the system by jointly optimizing the flight trajectory of the unmanned aerial vehicle (UAV), the uplink transmission power of ground nodes (GN), and the phase shift matrix of IRS. By reason of the coupling of optimization variables, the problem is a non-convex optimization problem. To address this issue, we propose an efficient robust iterative optimization algorithm. The simulation results show that by deploying IRS, the impact of interference on system transmission information is reduced and the average throughput is optimized.