Abstract: By collecting surface seawater near Shandong Peninsula, then analyze the surface distribution of ¹³⁷Cs, the data is combined with the East China Seas to explore the factors affecting the distribution of ¹³⁷Cs. The conclusions are as follows:(1) ¹³⁷Cs activity in study area ranges from 0.60±0.18 Bq/m³ to 1.21±0.19 Bq/m³, with an average of 0.90±0.17 Bq/m³. And ¹³⁷Cs activity of near shore is lower than offshore, mainly effected by coastal current; (2) The spatial distribution of ¹³⁷Cs in East China Seas are influenced by uneven distribution of the atmospheric deposition, coastal flow, river dulite water in seawater. The value of ¹³⁷Cs decreased sequentially and the Chernobyl accident has less impact on East China Seas; (3) The removal rate of ¹³⁷Cs in Bohai Sea is 0.046/a, which is higher than the Yellow Sea (0.032/a) or East China Sea (0.027/a), because of more scavenging and stronger horizontal and vertical mixing of water masses.