Unmanned aerial vehicle （UAV） communication and intelligent reflecting surface （IRS）-aided communication are typical air-ground transmission scheme in 6G mobile communication systems. It is available to enhance transmission performance of air-ground communication networks with cooperation of UAVs and IRSs. In this paper， by cooperating full-duplex UAV relay with passive reflecting of IRS， power control of the transmitter and reflecting element number of IRS are jointly optimized to improve energy efficiency. The simulation results show that the proposed method converges quickly and outperforms the UAV-relay-only and IRS-aided-only schemes.