Deep ocean circulation is widely considered as one of the important factors for increasing CO2 concentration and decreasing radiocarbon activity (C-14) of the atmosphere during the last deglaciation. The AMS C-14 ages of benthic and planktonic foraminifers from 18 samples of Core MD05-2904 (water depth of 2066m) in the northern South China Sea (SCS) and 15 samples of Core MD05-2896 (water depth of 1657m) in the southern SCS were analyzed in this study for reconstructing the intrabasin deep oceanic processes and hence exploring the deep water exchanges between the SCS and the Pacific since the last glacial period. The results show that during the Holocene the average apparent ventilation age of deep water was younger in the southern SCS (1350years) than in the northern SCS (1850years) due to relatively strong vertical mixing and advection, consistent with modern observations. However, during the last glacial period and deglaciation the deep water was older in the southern SCS (2050years and 1800 to 1200years, respectively) than in the northern SCS (1600years and 670years, respectively), indicating reduced deep mixing and advection. Moreover, the northern SCS deep water was significantly younger during the last deglaciation than during the Holocene and the last glacial period, implying the existence of northern sourced newly formed and relatively young North Pacific deep water. Our records do not support the intrusion of anomalously C-14-depleted deep water to the middepth of the low-latitude western Pacific and the SCS during the Mystery Interval (17.5-14.5 kyr B.P.).