The Changjiang diluted water (CDW) is formed by the mixing of the Changjiang runoff with the East China Sea water. The distribution of the CDW shows several low salinity patches, i.e., not a single tongue shaped pattern. The typical lateral scale of a low salinity patch is about 100 km/2 psu. Some patches show a bowl shaped distribution pattern in the vertical with a clear surface low salinity core. As an example, in August 1996, the extremely low salinity core with 20 psu appeared in the region west of Cheju-do. The CDW moves to the east and northeast towards Cheju-do in summer. Recent observations of satellite-tracked drifters indicate that the movement of the CDW depends largely on the wind system (Lee et al. 2003, Lie et al., 2003). Although it is now understood the basic behavior of the CDW, detailed description of the CDW is far from complete. In order to investigate the behavior of the CDW, KORDI conducted hydrographic survey in the northern East China Sea in July 2004. Seven satellite-tracked drifters were deployed during the survey period jointly with Cheju National University, Pusan National University and Kyushu University. This presentation reports the preliminary results.