Abstract: In deep-ocean reliable acoustic path (RAP) environments, active sonar detection is often constrained by strong reverberation, while existing time- or frequency-domain processing methods have difficulty separating target echoes from reverberation effectively. To address the annular spatial structure of sea-surface-scattered reverberation in RAP environments, this paper proposes a harmonic-domain spatial direct-current (DC) component suppression method. The proposed method is independent of specific waveform design. Instead, it exploits the spatial structural difference between annular reverberation and target echoes. Specifically, the dominant reverberation component is predominantly concentrated in the zeroth-order harmonic, which is selectively suppressed to reduce the reverberation background while preserving the higher-order spatial components of the target echo. Numerical simulations and sea-trial data processing results show that, compared with conventional beamforming and the phase-mode method, the proposed method effectively reduces the reverberation background energy under low signal-to-reverberation ratio conditions, enhances the target bearing spectral peak, and preserves the time-frequency structure of the target echo.