Aiming　at　the　difference　in　number　of　users　in　busy　time　and　spare　time　for　the　femto　base　station　(FBS),　the　power　allocation　problem　of　maximizing　the　total　downlink　information　is　investigated　in　this　paper.　By　deploying　a　pico　base　station　carried　by　unmanned　aerial　vehicle　(PBS-UAV),　it　provides　services　for　users　of　multiple　FBSs　in　spare　time.　Both　the　FBS　and　PBS-UAV　have　energy　harvesting　function.　During　the　busy　time,　the　FBS　and　PBS-UAV　simultaneously　harvest　energy　from　the　macro　base　station,　and　FBSs　transmit　data　to　users.　During　the　spare　time,　multiple　FBSs　are　replaced　by　the　PBS-UAV　to　communicate　with　users　in　downlink.　The　power　allocation　problem　is　modeled　as　an　optimization　problem.　The　objective　is　to　maximize　the　amount　of　downlink　information　of　FBSs　and　PBS-UAV　while　satisfying　the　constraints　of　FBS　and　PBS-UAV　energy　consumption　and　transmission　power.　The　optimal　solution　is　obtained　by　using　an　augmented　Lagrange　multiplier　method.　The　simulation　results　show　that　compared　with　the　equal　power　method　and　partial　fixed　power　method　with　PBS-UAV,　the　proposed　method　has　an　increase　in　terms　of　total　information　to　different　degrees.　©　2020　IEEE.