<p>The control approaches based on disturbance observers has great application potential. However, it places high demands on the accuracy of the disturbance observer, which relies on high-frequency transmission of sensor information for precise estimation. In networked systems with limited communication resources, it is unrealistic to obtain real-time sensor measurements. To achieve good estimation performance of the disturbance observer while reducing data transmission frequency, an event-triggered compensation function observer (ET-CFO) is proposed. Through Lyapunov stability analysis, the estimation error of the ET-CFO is shown to be bounded, and the quantitative relationship between the observer’s accuracy and parameter selection is revealed. To validate the proposed method, the designed ET-CFO is applied to estimate disturbances and uncertainties in the attitude subsystem of a quadrotor unmanned aerial vehicle (QUAV). Simulation results demonstrate that the ET-CFO can maintain estimation accuracy while reducing the data transmission frequency. As the triggering frequency increases, the performance of the ET-CFO becomes comparable to that of the standard CFO.</p>