The East China Seas （Bohai，Yellow，and East China seas)（ECSs），an important linkage between the global largest continent （Eurasia）and the ocean（Pacific），annually received more than 1.7 billion tons of sediment from the adjacent rivers. These huge amounts of fine grained material，combined with the effects of tide，wave/storm and current，contributed to several muddy depositional areas in the broad and shallow shelf of ECSs. During the last several decades，many papers have been released and focused on sediment dispersal and sediment dynamics in the ECSs shelf. However，little is known relevant to the modern sedimentation flux （SF） and budgets in this large continental marginal sea system. In this study，on the basis of a number of 137Cs~and 210Pb~derived sediment accumulation rate （SR） data，we firstly evaluated the modern SR and SF over the entire muddy areas of the ECSs shelf，and then calculated a sediment budget for the muddy areas of ECSs shelf to assess whether the sediment mass （input from rivers vs. accumulation flux） is balance or not. We also compared the Modern and Holocene sediment accumulation rates （millennial~scale） in different muddy areas. The results show that sediment source is a dominant factor controlling the formation of these muddy areas of the ECSs shelf. The sediment delivered by adjacent rivers is the major sediment source，whereas the muddy areas of the ECSs shelf are typical sediment sink. We emphasized the role of small rivers in the sedimentary process of the local river estuaries and its contribution to the muddy areas. A quantitative sediment provenance study should be conducted by considering constrains of sediment source and sediment mass balance.