The Huanghe and Changjia paleo-rivers developed before high sea level in Holocene formed a broad fluvial plain and river mouth delta on the South Yellow Sea continentai shalf. Use of high resolution geophysical instruments revealed buried the Huanghe and Changjiang paleo-rivers valleys at more than 100 stations. The old Huanghe River which formed after high sea level in Holocene and before change of it's course in 1855 A D, emptied through the Subei Plain into the South Yellow Sea for 700 years resulting in formation of the accumulation shore plain of 104km2 and the north old Huanghe-changjiang combined delta of 3*104km2，besides, the old Huanghe River transported (250-400*104t/a) sediment to the center part of the South Yellow Sea to form thin Holocene sediment layer. More than 99% of the sediment load from the modern Huanghe River deposited in the Bohai Sea. Less than 1% is transported and round the Chengshan Cape to affect the northwest part of the South Yellow Sea. However there is only small immediate influence on the center and deeper part because of the presence of the Huanghai Cold Water Mass. Sediment loads from the modern Changjiang River were mainly transported southeastward and eastward. A part of it can be carried into the South Yellow Sea. The South Yellow Sea historically was a mixed deposition area of sediment from the Huanghe and Changjiang rivers, but the modern accumulation rate is small.