This paper considers an event-triggered sliding mode control approach for quadrotor unmanned aerial vehicle (UAV) to solve the trajectory tracking control problem under communication resource constraints. Firstly, the rigid-body dynamics model of the quadrotor is analyzed and briefly described event-triggering mechanisms (ETM) for general non-linear systems. Separate controllers were designed for the position and attitude of the quadrotor, and analysed the stability of the closed-loop system using Liapunov theory. Then, it is proved that Zeno phenomenon does not exist When closed loop controlling. The simulations verify that the proposed method can effectively reduce the number of controller updates while maintaining good trajectory tracking efficiency of the quadrotor UAV under different tracking commands. Meanwhile, it reduces the amount of controller computation and improves the system resource utilization.