Based on temperature and salinity data gathered from 1963 through 1986 in the Yellow Sea and the East China Sea in summer, the distributional characteristics of the inverse structure of the temperature and salinity and its formative causes are analysed in this paper. Some results show that (1) the inverse structure in summer can be found in three regions, the area of the Zhejiang Coast upwelling, the area of the cold eddy in the northern part of the East China Sea and the area of cold water mass in the southern Yellow Sea, (2) the inverse structure in above three areas can be separately caused by the wind, the vertical circulation in the area of the cold eddy,and the northward extension of the Huanghai warm current water which is warmer and more saline in bottom.