Abstract: To solve the problem of depth resolution of broadband sound sources in typical deep-sea environments,a broadband source depth estimation method for distinguishing multiple underwater targets is proposed.The interference pattern structure of acoustic field in direct zone of deep waterwith frequency fluctuation and the beam output of a vertical array in frequency domain are studied.Based on the ray theory of near-surface target,the beam output expression of broadband propagated sound field is deduced,and the corresponding relationship between interference pattern structure and source depth in frequency-domain beam output is clarified.Then,the modified Fourier transform method is used to map the two-dimensional frequency-domain beam output map to the depth-pitch angle space of the sound source,which can effectively separate the depth information of the sound sources.Finally,deep-sea experiments are carried out to verify the consistence between the depth of the towed source and the measured depth of the source by using the broadband white noise signal emitted by the towed source and received by the vertical array.Both numerical simulation and experimental results show that this method can accurately estimate the depth of underwater broadband sound source under multi-target complex environment.