The dynamics of pore water salinity and sediment saturation degree are critical factors influencing fluid flow during gas hydrate production and seawater intrusion in marine environments. The percolation capacity of pore fluids is closely related to the soil water characteristics curve (SWCC). However, the influence of pore water salinity and clay mineral type on the SWCC of marine sediments remains poorly understood. This study investigates these effects through centrifuge tests on laboratory sand- clay mixtures and desalted marine sediments collected from the northern South China Sea (SCS), a region with natural gas hydrate occurrences. Pore water saturation was meticulously measured under varying matrix suctions conditions. Subsequently, the influence of pore water salinity and clay mineral type on the SWCC were systematically analyzed, followed by curve fitting using the van Genuchten model. The findings revealed that the SWCC of artificial quartz sands containing 20% clay by weight exhibited negligible dependence on the clay mineral type. Despite the clay content exceeding 35%, the SWCC of natural marine sediments from the northern SCS exhibited minimal variation when subjected to changes in pore water salinity. Upon applying the van Genuchten model to these natural marine sediments, the following parameter values were obtained: a=0. 00023 kPa-1, n=0. 51, and m=4. 9.