Abstract: In order to understand the paleo-environmental evolution in the northern South China Sea (SCS) since the last interglacial, the compositions of C-O isotope, calcium carbonate, total organic carbon (TOC) and grain size for sediments in Core 83PC derived from the Xisha trough were investigated. The results showed that the δ¹⁸O and δ¹³C values of planktonic foraminifer exhibited significant glacial-interglacial cycles, controlled by the sea level fluctuation and climate change. The input of terrestrial materials increased during glacial sea level fall, and the sediments had lower carbonate content and higher TOC content; however, it decreased during interglacial sea level rise, and the sediments had higher carbonate content and lower TOC content. The chemical composition of sediments in core 83PC indicates climatic instability in late Pleistocene; and rapid climate changes and low carbonate sedimentation could be identified. The low carbonate contents at depth of 150 cm, 510 cm, 660 cm and 740 cm is thought to be an evidence for the occurrence of global cooling events. And a rapid decrease in carbonate content during early-middle post-glacial period might be resulted from the changes in rainfall. Erosion would be intensified wile heaop rain, and the dilution effect to carbonate wap thus enhanced.