Abstract: The characteristics of ocean currents at different depths in the deep-water region of the northern South China Sea are analyzed based on the data of continuous near-full-depth current observation carried out by means of a subsurface mooring system from July 2022 to September 2023. The results indicate that the ocean currents in the study area are relatively stronger at the water depths shallower than 500 m and exhibit a good consistency at the water depths deeper than 1 000 m, with the predominant ocean current being of baroclinic type. The tidal currents in the study area are dominated by diurnal tidal current and the semidiurnal tidal current is significantly weaker than the diurnal one so that the tidal currents in the study area are mainly of an irregular diurnal type. The tidal constituents O₁ and K₁ rotate primarily clockwise, while the constituents M₂ and S₂ rotate mainly counterclockwise. The orientation of the major axis of the tidal current ellipse varies with water depth: it is dominated by E-W direction at a water depth of 130 m (but the tidal constituent O₁ flows along N-S direction), and turns to ENE-WSW and NE-SW directions at the water depths deeper than 1 000 m. Tidal kinetic energy is relatively stronger 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% at the depths deeper than 2 000 m. The tidal kinetic energy significantly varies with seasons. Except near a water depth of 1 000 m, the tidal kinetic energy at all other depths reaches its maximum value at the beginning of summer (June 2023) and exhibits a weaker peak from late autumn to winter (November 2022 to February 2023).