Dear　Editor,
This　letter　addresses　the　predefined-time　control　for　cooperative　tracking　of　multiple　quadrotor　unmanned　aerial　vehicles(UAVs)under　a　directed　communication　network.A　predefined-time　dis-tributed　estimator　is　first　introduced　to　accurately　get　the　reference　velocity　and　acceleration　for　each　UAV.Then,a　cascade　predefined-time　control　strategy　is　proposed　to　guarantee　that　all　the　UAVs　track　the　reference　trajectory　while　maintaining　a　preassigned　configura-tion,where　an　attitude　constraint　algorithm　is　developed　to　avoid　the　flipping　over　of　each　UAV.Stability　analysis　demonstrates　that　the　tracking　errors　of　the　closed-loop　systems　converge　to　zero　within　a　predefined　time.Finally,experiment　results　validate　the　proposed　control　strategy.