Considering　that　unmanned　aerial　vehicles　(UAVs)　with　the　advantages　of　flexible　deployment　and　high　maneuverability　have　the　limited　energy　to　provide　long-term　seamless　coverage,　a　cooperative　recharging-transmission　strategy　is　studied　in　this　paper　for　the　powered　UAV-aided　terahertz　(THz)　downlink　networks,　where　a　UAV-to-user　THz　sub-band　association　scheme　is　proposed　for　the　THz　frequency　transmission　to　eliminate　interference.　Based　on　this,　the　minimum　requirements　of　the　wireless　charging　window　and　THz-transmitting　window　are　derived.　A　minimization　problem　of　minimum　timeslot　requirement　is　formulated　to　jointly　optimize　UAV　placement　and　UAV-to-user　THz　sub-band　association.　The　optimization　problem　is　non-convex,　and　we　propose　an　alternating　optimization　solution　via　iteratively　solving　placement　subproblem　and　association　subproblem.　Specifically,　we　resort　to　the　coalescent　method　of　interior　point　and　gradient　descent　algorithms　to　optimize　UAV　placement.　The　UAV-to-user　THz　sub-band　association　is　solved　as　a　knapsack　problem　by　the　transformation　of　association　matrix.　Simulation　results　validate　the　solution　and　demonstrate　that　the　proposed　strategy　can　achieve　quasi-optimal　performance　compared　with　other　contrasting　strategies.