Abstract: In the deep water environment, a horizontal line array is incapable of distinguishing the bearing angle and elevation angle of the incident sound wave due to its array characteristics, resulting in the significant systematic error in target direction of arrival estimation, especially in the shadow zone that contributed by the eigenrays with large launch angle. To address the problem, the formation mechanism of the bearing estimation error is derived based on the ray model and the constraint relationship between estimated target bearing, true target bearing and target elevation angle is deduced. Secondly, a modified DOA estimation method for the target in the shadow zone of deep water is proposed in this paper. Based on the one-to-one corresponding relationship between the elevation angle and horizontal range in the shadow zone, the elevation angles are introduced into the beamforming to correct the weighted vector, which has well improved the accuracy of target bearing estimation in the shadow zone of deep water. Numerical simulations validated the effectiveness of the proposed method and the performance of the method are also analyzed. The sea experiment shows that the proposed method successfully achieves bearing estimation of target in shadow zone, further verifying the effectiveness of the method.