For the quadrotor with model uncertainty and quantised input, this paper proposes a new control strategy by combining fixed-time command filtering with backstepping under quantised input. Firstly, the virtual control signal in the traditional backstepping method is used as the input of fixed-time command filtering, so that the derivative of the virtual control signal can be obtained directly, which effectively avoids the problem of ‘differential explosion’ brought by the traditional backstepping method, and the filtering error compensation signal is designed to fill the defect that the filtering error affects the system performance. Then, an adaptive law for the quantisation parameters is designed, which can still be applied when the a priori information of the quantisation parameters is uncertain. Then, it is verified that all the signals in the closed-loop system are bounded at fixed time, and the position and attitude tracking errors of the quadrotor can reach a sufficiently small region of the origin at fixed time. Finally, simulation experiments are given to verify the feasibility and superiority of the control method.