This paper investigates an event-triggered based robust finite-time trajectory tracking control problem for quadrotor unmanned aerial vehicle (QUAV) subject to external disturbance and input saturation. Firstly, nonlinear disturbance observer and parameter adaptive method are designed to remove the adverse effects of unknown external disturbance and input saturation, respectively. On this basis, a backstepping based finite-time robust tracking controller is presented to realize trajectory tracking control. In addition, an adaptive event-triggered mechanism is implemented  to reduce the signal transmission burden. The stability of the system is guaranteed by the Lyapunov theorem. Finally, the effectiveness of the proposed trajectory control scheme is verified by simulation tests for the QUAV dynamic system.