The potential application of the cosmogenic nuclide ¹⁰Be in marginal seas and island-arc system study has been discussed. Dissolved beryllium-10 concentration profiles in seawaters of the East China sea and the Kuroshio have been investigated. The results show that ¹⁰Beconcentrations in this area are mainly controlled by surface biological productivity, partical remineralization, and the degree of mixing with Changjiang River (the Yangtze river) and  Kuroshio waters. Generally the¹⁰Be water depth profiles can be divided into three layers: the surface mixing layer, the particulate ¹⁰Be regeneration layer and the bottom layer. Surface water¹⁰Be concentrations increase gradually towards the Okinawa Trough and increase sharply at the edge of the Kuroshio Current. Vertical distributions of ¹⁰Be show that ¹⁰Be is enriched in the bottom waters near the Yangtze river estuary and the central continental shelf. Box model results indicate that ¹⁰Be input from the Kuroshio current is more important than Yangtze river input and atmospheric precipitation. About 81% of the¹⁰Be input to the East China sea is scavenged into the sediments and 19% of the ¹⁰Be flows out of the East China sea by currents and water exchange. The¹⁰Be sedimentation flux in the East China sea is nearly five times of the average global ¹⁰Be production rate. Therefore the East China sea may be an important sink for  ¹⁰Be.