A three dimensional baroclinic prognostic model on σ-coordinates was established on the basis of POM to simulate the East China Seas circulation in summer considering the topography, inflow and outflow at the open boundary, Changjiang runoff, heat flux and wind stress on the surface. This study showed that ① the Kuroshio flows along the continental shelf slope of the East China Sea flowing in accordance with the slope topography and some eddies appear on its two sides; ② the upper water of the Taiwan Warm Current comes mainly from the Taiwan Strait and that the bottom water comes mostly from Kuroshio sub-surface water flowing on the shelf and passing through the east of Taiwan Island; ③ the Tsushima Warm Current in summer comes from multiple sources: the Taiwan Warm Current, one of the branches of the Kuroshio, mixed water of Changjiang Diluted Water with West Korea Coastal Current and Taiwan Warm Current; ④ the Changjiang Diluted Water turns northwards rapidly after flow sing out the Changjiang River Mouth, affected by Zhejiang Coast Current, Taiwan Warm Current and southwest monsoon, and flows southeastwards after arriving at around 34°N; ⑤ there is a meso-scale anticyclonic eddy in the northeast of the Changjiang River Mouth it was formed by the north branch of the Taiwan Warm Current and there is another cyclonic eddy in southwest of Chejudo Island; ⑥ the circulation of the Huanghai Cold Water Mass in summer is divided into north and south parts and their current is strong in the upper layer and weak near the bottom layer; ⑦ there is a meso-scale anticyclone eddy near the Qingdao- Shidao coast area.