Abstract: This paper analyzes the observed characteristics of ocean currents at different depths in the deep-water region of the northern South China Sea, drawing on continuous near-full-depth ocean current observation data obtained from a subsurface mooring system from July 2022 to September 2023. The observation results indicate that the ocean currents in this region are relatively strong at depths shallower than 500 m and exhibit greater consistency below 1 000 m, with baroclinic currents being the predominant type. The diurnal tidal currents dominate in this area, with the semidiurnal tidal currents being notably weaker than the diurnal ones, so that the tidal currents are classified primarily as the irregular diurnal type. The tidal currents of the O₁ and K₁ constituents predominantly rotate clockwise, while those of the M₂ and S₂ constituents mainly rotate counterclockwise. The orientation of the major axis of the tidal current ellipse varies with depth: it is mainly E–W at 130 m (N–S for the O₁ constituent), and turns to ENE–WSW and NE–SW below 1 000 m. Tidal kinetic energy is relatively strong at depths shallower than 500 m, accounting for approximately 10%–15% of the total kinetic energy, and its proportion in the total kinetic energy exceeds 30% below 2 000 m. There is a pronounced seasonal variation in tidal kinetic energy; apart from at the 1 000 m depth, tidal kinetic energy at all other depths reaches its maximum in early summer (June 2023) and exhibits a weaker peak from late autumn to winter (November 2022 to February 2023).