Aiming at the problem that current damping technology for inertial navigation system based on Kalman filter depends on the ground velocity， a horizontal damping method for inertial navigation system based on adaptive delayed state filter is proposed. In this method， a delayed state is introduced so that the ground velocity is not included in the measurement equation. And the measurement noise adaptive theory and delay state filter theory are combined to improve reliability. It is suitable for the damping process of inertial navigation system under the condition that only the water speed can be obtained. Simulation experiments show that the proposed method can use water velocity to achieve damping for system error.