Abstract: This paper proposes a robust fault diagnosis method of actuator in nonlinear-time-delay system with uncertainties. The nonlinearity is related with both inputs and outputs, the uncertainties include states and output. The observer techniques and adaptive techniques are used to obtain values of system output and estimated output. The fault occurs if the difference between them equals or exceeds the threshold. Robustness, sensitivity and stability are analyzed. At last, this method is validated through simulation.