Abstract: A robust H^∞ filter is developed for the heading control system of an autonomous underwater vehicle(AUV) to estimate some state variables which are not always available and are often difficult to measure in practice,and we extend the filter’s application to the AUV heading control system.The equations of the AUV motions in the body-fixed horizontal plane are established,and they are linearized over a specified operating point to suit for the controller design.A robust H^∞ filter for the AUV heading control system is designed based on the method of linear matrix inequalities(LM Is),and its application to the AUV heading control system is simulated by computer.The simulation results show that the proposed robust H^∞ filter is effective to reject the negative effects of measurement noise and properly estimate the state variables of the system,and it makes much contribution to the performance improvement of the AUV heading control system.