Abstract: Main sediment components in the modern upwelling area of the southwestern South China Sea during the last 140, 000 years were analyzed for a gravity core retrieved by the SONNE 187 cruise in 2006, aiming to reveal the marine environmental changes in the southwestern South China Sea since the last interglacial. During the last 140, 000 years, the mass percent of carbonate was generally high in interglacial but low in glacial periods, as the typical "Atlantic type of carbonate", suggesting strong influences of the terrestrial input in the southwestern South China Sea. Relatively high accumulation rate of organic carbon, biogenic opal and lithogenic components was found in MIS 2 and MIS 4, related to the enhanced primary productivity provoked by the increase in terrestrial input nutrients, as a result of strengthened winter monsoon and the decline of sea level during the ice age; It might also be related to the enhanced ballast effect of the lithogenic matters of sinking particles during the ice age. At the peak of the last interglacial period (MIS 5e), strengthened upwelling off Vietnam coast induced by stronger summer monsoon was responsible for the increase in primary productivity and accumulation of both biogenic and lithogenic sediments.