Based on the detailed planktonic foraminifera faunal count and Globigerinoides ruber Mg/Ca ratio analysis of Core MD05-2901,we reconstructed the longest Mg/Ca sea surface temperature(SST) sequence of the upwelling area off Vietnam in the western South China Sea(SCS).Ocean environment,especially the SST variation,over the last 450 ka is discussed in this study.SST variation has typical glacial/interglacial alternations from 23.03°C to 29.93°C with a glacial/interglacial difference of 4.8°C on average.SST during the interglacial periods fluctuates significantly,up to 5.6°C,which is larger than the average glacial/interglacial difference.SST variation during the glacial periods is much smaller.Spectrum analysis shows that SST change dominates on the typical Milankovitch cycles,such as 112,40.7 and 23.6 ka.Evident leading of SST variation against the δ 18 O can be observed during the Terminations 1,4,and 5,which is confirmed by their cross-spectrum analysis on these cycles.MD05-2901 is the first core in the South China Sea that has multi-SST records,such as SST Mg/Ca,k’ 37 U-SST and planktonic foraminiferal fauna-based SST.SSTs from different methods can be correlated with each other in glacial/interglacial time scale,whereas SST Mg/Ca records abrupt climate change events more clearly.SST Mg/Ca at MD05-2901 since MIS 5 is 0.6°C lower than that of the southern SCS on average,but equivalent to or even 2°C lower than that of the northern SCS during some interglacial period.The SST character of MD05-2901 reflects less influence of latitude,but an important role of the regional upwelling driven by the eastern Asian summer monsoon,and suggests a stronger upwelling during the interglacial periods in the western SCS. Based on the detailed planktonic foraminifera faunal count and Globigerinoides ruber Mg / Ca ratio analysis of Core MD05-2901, we reconstructed the longest Mg / Ca sea surface temperature (SST) sequence of the upwelling area off Vietnam in the western South China Sea (SCS ) .Ocean environment, especially the SST variation, over the last 450 ka is discussed in this study. SST variation has typical glacial / interglacial alternations from 23.03 ° C to 29.93 ° C with a glacial / interglacial difference of 4.8 ° C on average. SST during the interglacial periods fluctuates significantly, up to 5.6 ° C, which is larger than the average glacial / interglacial difference. SST variation during the glacial periods is much smaller. Spectrum analysis shows that SST change dominates on the typical Milankovitch cycles, such as 112, 40.7 and 23.6 ka. Evident leading of SST variation against the δ 18 O can be observed during the Terminations 1, 4, and 5, which is confirmed by their cross-spectrum analysis on these cycles. MD05-2901 i s the first core in the South China Sea that has multi-SST records, such as SST Mg / Ca, k ’37 U-SST and planktonic foraminiferal fauna-based SST.SSTs from different methods can be correlated with each other in glacial / interglacial time scale, while SST Mg / Ca records abrupt climate change events more clearly. ST Mg / Ca at MD05-2901 since MIS 5 is 0.6 ° C lower than that of the southern SCS on average, but equivalent to or even 2 ° C lower than that of the northern SCS during some interglacial period. the SST character of MD05-2901 究 less influence of latitude, but an important role of the regional upwelling driven by the eastern Asian summer monsoon, and suggests stronger than literally during the interglacial periods in the western SCS.