This paper investigates the predefined-time formation control of quadrotor unmanned aerial vehicles (QUAVs) under input saturation constraints. To mitigate the effects of input saturation, an auxiliary system is meticulously designed. In contrast to other studies which merely attain the asymptotic stability of the auxiliary signals, the auxiliary system proposed ensures the predefined-time stability, thus contributing the stability of entire system. Subsequently, based on the predefined-time stability criterion, a distributed formation controller is developed, thus guaranteeing the predefined-time stability and robustness of formation under input saturation. Finally, simulations validate the effectiveness of the proposed method.