The restoration of Cheonggyecheon was a project which creates a refreshing water-friendly environment in the downtown Seoul. It already have passed almost 2 years after restoration. This project changed environment of Cheonggyecheon dramatically, so historic hydrological data became useless. There are not so many hydrological data to manage and control this newly restored urban stream. The main purpose of this study is collecting and analysing the hydrological data of Cheonggyecheon. At first, we analysed the mechanism of Cheonggyecheon discharge using the sewage design maps and some GIS data. We also monitored the water levels and discharges of 5 main points of Cheonggyecheon. Rating curves of these 5 points were derived. In additions, we also monitored the behaviors of water gates which were located at both sides of bank. There were 249 blocks of water gates. Through the this monitoring, some equations were derived to give useful information to the manager of Cheonggyecheon