Abstract： Based on nonlinear model for ship motion, making use of the characteristic of sliding mode control, the automatic motion control on ship course change was studied. In view of the interference of waves, and considering the design principles of nonlinear disturbance observer and the characteristics of interference suppression for extended state observer, a novel extended state disturbance observer was designed, which can compensate for the external interference and reduce the shake impact of slidingmode control. The analysis shows that the system ensures the reliability of ship course system and weakens the volatility about course change. The simulation verifies that the system can achieve stable control of the ship course control.