Abstract: For the application of vector hydrophone in bearing estimation, effects of horizontal refraction on vector-field characteristics in the problem of three-dimensional(3 D) underwater sound propagation are studied. Through theoretical analysis, it is shown that with the presence of horizontal refraction, the horizontal displacement is elliptically polarized,which shall be linearly polarized provided there is no horizontal refraction. Simultaneously, the direction of the horizontal component. of sound energy flux is deflected due to horizontal refraction, resulting in a deviation of the signal arrival direction from the source bearing and thus arising error of bearing estimation. The 3 D vector fields in a series of wedgelike oceans are calculated with the method of source images, and the bearing estimation errors are shown to be larger than 10° in some areas.