Abstract: Sound scattering is an important acoustic phenomenon. High-frequency acoustic scattering signals generated by seawater bodies can be used to conduct acoustic oceanographic research for various purposes and may interfere with the underwater acoustic equipment. However, the background sound scattering of seawater bodies is characterized by significant spatial and temporal variations. As a result, it is of great significance to carry out the observations of time-varying sound scattering in a specific sea area. In this study, sound scattering data of 80 days covering four seasons are collected by using two ADCPs equipped in a mooring system in the Northern South China Sea. The data include two frequency bands of 75 kHz and 300 kHz and involve almost the whole water column from the surface to about 600 m deep. There exist two acoustic scattering layers in the vertical direction of the water column: one is the upper scattering layer, which is distributed at a water depth shallower than about 100 m in winter and summer and about 200 m in spring and autumn, and the other is the lower scattering layer, which lies at a water depth deeper than about 300 m in winter and about 400 m in summer. Therefore, the distance between the two scattering layers is the farthest in summer and the closest in spring and autumn. The acoustic scattering intensity in the two scattering layers also shows significant seasonal variations. In the upper layer the acoustic scattering intensity is stronger in summer and autumn and weaker in spring and winter, whereas in the deep layer the acoustic scattering intensity is exactly the opposite.