This paper investigates the flexible satellite attitude control system (ACS) with time delay, actuator fault and disturbance. Based on robust control technique, a control strategy is proposed to improve the performance of ACS; meanwhile, the disturbance and actuator fault are estimated accurately by composite observer. Specially, the correlative factor of time delay is built to decrease the impact of time delay on flexible satellite ACS. And lastly, the effectiveness of the presented method is illustrated by simulations.