The correlation of opal content and MAR with oxygen isotopic records of benthonic foraminifera at Site 1143, southern South China Sea indicates that, since about 900 ka, the increasing opal content and MAR during the interglacial periods is inferred to reflect the higher surface productivity, for the intensified summer monsoon during the interglacial periods would result in the enhanced upwelling and nutrient supply. Time-sequence spectral analyses of oxygen isotopic record, opal content and MAR at intervals of 0-900 ka reveal that the changes of surface productivity were dominantly forced by the variations of the earth orbital cycles.