Sediments with high sedimentation rate at Site MD05-2905 in the northern part of the South China Sea provide unique materials for a high-resolution study on paleoenvironment. Based on precision dating of AMS14C, grain size analysis of terrigenous clast at Site MD05-2905 is studied after removing organic matter, biological carbonate and biogenic opal. The results show that 15.5~63.5μm, coarse grain size ingredients，may indicate the East Asian winter monsoon changes. And that 2 ~ 9μm，fine grain size ingredients，may be used as a proxy of evolution of the East Asian summer monsoon. The results of grain size analysis, which suggest the East Asian monsoon intensity, revealed that a winter monsoon dominated glacial regime and a summer monsoon dominated Holocene regime, and that the summer monsoon increased gradually，experienced several abrupt change events and reached to the culmination in the early Holocene（8 500~11 200 ka BP） after 36 ka. This, with control by precession periodicity, may be related with the amount of solar radiation at the highest stage which needs further study.