This paper focuses on large-angle trajectory tracking control of a quadrotor in discrete time domain.Firstlythe Newton-Euler method is used to establish a dynamic model based on 3D rotation group SO(3)which is then transformed into a discrete-time model by using the forward Euler method.Nexta control scheme based on the structure of inner and outer loops is proposed.Thendiscrete-time sliding mode control is applied to the design of inner and outer loop controllerswhose stability is proved by Lyapunov function.Finallythe performance of the designed control system is verified by Matlab simulation.The simulation results show that the designed control system has good large-angle trajectory tracking performance.