The vertical characters of temperature, salinity and density fluctuations in shallow region of the East China Sea are analysed by using 12 CTD short records with 1-hour intervals. The average S,t and p profiles can be divided into three distinctive layers: the thermocline, and the layers above and below it. The fluctuations of t, S and p are basically caused by internal waves, but there are somewhat intrusions or entrainments at the thermocline boundaries. The vertical displacement of the thermocline centre is up to more than 6.35m and the thermocline thickness changes from 3.5 to 8.0 m. Their varature with time are intermittent and rather irregular. The vertical wavenumber spectra of temperature fluctuations have been estimated by using the maximum entropy method, indicating that energy is mainly contained in the low-wavenumber range (<0.13cpm) with two sharp peaks probably corresponding to the first and second modes of internal waves, whose dependence is estimated to be less than β-2. There exist dep The vertical characters of temperature, salinity and density fluctuations in shallow region of the East China Sea are analyzed by using 12 CTD short records with 1-hour intervals. The average S, t and p profiles can be divided into three distinctive layers: the thermocline , and the layers above and below it. The fluctuations of t, S and p are so caused by internal waves, but there are somewhat intrusions or entrainments at the thermocline boundaries. The vertical displacement of the thermocline center is up to more than 6.35m and the thermocline thickness changes from 3.5 to 8.0 m. Their reaction times are intermittent and rather irregular. The vertical wavenumber spectra of temperature fluctuations have been estimated by using the maximum entropy method, indicating that energy is mainly contained in the low-wavenumber range (<0.13 cpm) with two sharp peaks probably corresponding to the first and second modes of internal waves, whose dependence is estimated to be less than β- There exist dep