In summer there is a cold water mass located at the depth from the thermocline to the bottom southwest of the Cheju Island on the northern shelf in the East China Sea. This paper names it “the Northern Bottom Cold Water Mass in the East China Sea”(simply called the “Northern Bottom Water”in the following). Using the data of 1963-1977, the authors obtained some results,such as the distribution of the Northern Bottom Water and the processes of its occurrenee, formation and disappearance, and also discussed its central position at section 32°N, its east and west boundary，and its spreading area. Besides, the cause that led to the formation of the Northern Bottom Water was also analyzed. It was primarily concluded that the Northern Bottom Water was the same water left over from winter without obvious increase of temperature. The density circulation of the Northern Bottom Water was briefly discussed,which showed that there was a weak anticlockwise cireulation at its upper layer in June, 1976, but a clockwise cireulation to the southwest.