On the basis of CTD data obtained in the large-scale hydrologic investigation carried out in the northern East China Sea shelf in June of 1984 and 1985 by the Institute of Oceanology,Chinese Academy of Sciences, BT data obtained during 1975-1980 by the State Oceanic Administration in sectional observation in the East China Sea, inversion phenomena (and its cause of formation )of temperature and salinity in the northern East China Sea shelf and the geographic distribution for every characteristic value of the inversion layer of temperature and salinity were analysed and studied. The results in question show that the inversion structural fields of temperature and salinity in the northern East China Sea shelf are basically distributed in the vast sea area in the vicinity southwest off Cheju Island, then extends southeast and then turns south. There also exists yearly variations. The temperature inversion layers consist mainly of intermediate cold water; the inversion layers of salinity consist mainly of intermediate low salinity water, intermediate high salinity, and the alternately intermediate low and high salinity waters. The distribution characteristics for every characteristic value of inversion layer clearly showed that the stronger inversion layers in the structural fields are generally thicker. There is often simultaneous occurrence of inversion layers of temperature and salinity.