Summary The paper is devoted to the problem of control law optimization for marine ships, which are steered by autopilots under the action of sea disturbances, mainly determined by bias terms and high-frequency wave components. The essence of the problem is to find a transfer function of the adjustable corrective item (filter) for the autopilot with a special structure, minimizing the functional, which characterizes the intensity of a ship's rudders action. The correspondent dynamic of a closed-loop system provides an economical regime of the ship motion, with the aim to reduce general fuel consumption and to prevent the wear of actuator elements. A specialized approach to the filter design is proposed based on the modern H_∞ optimization theory, and its applicability and effectiveness are illustrated by the practical example of autopilot synthesis for a transport ship.