Planktonic foraminifers from ODP Site 1143, southern South China Sea (SCS), were analyzed to reveal their response to glacial cycles over the past 2.1 Ma. Pulleniatina obliquiloculata, a widely-accepted indicator of the Kuroshio, shows completely reversed fluctuations, with a high abundance in glacial periods in the southern SCS compared to those found in the Okinawa Trough and in the northern SCS since the Mid-Pleistocene Revolution (MPR). Before the MPR, P. obliquiloculata is abundant in interglacial intervals. Cross-spectral and phase analyses of P. obliquiloculata and delta (super 18) O confirm these observations. The authors ascribe the transition of P. obliquilaculata's response to glacial cycles in the southern SCS to a profound change in the regional upper ocean structure, probably related to glacial separation of the southern SCS from Indian water and to higher surface salinity during glacial times after the MPR.