This study was conducted around Nakdonggang Estuary located in Busan. The study aimed to figure out current state by conducting long-period monitoring of common goldeneye (Bucephala clangula) around Nakdonggang Estuary where surrounding environment is rapidly changing. The data recorded in the early 1990s (May, 1989~April, 1993) and in the mid-2000s (May, 2002~April, 2008) were compared and analyed. A total of 1,563 common goldeneyes were observed around Nakdonggang Estuary during the study period (total 10 years). It was shown that there was no significant difference in the visitation aspect during the early 1990s and the mid-2000s in monthly analysis of the visitation aspect of goldeneye(P>0.05), but the number of common goldeneyes was higher in the mid-2000s (mean=241.67) than that in the early 1990s (mean=28.25). In the comparison of annual average number of common goldeneyes during the early 1990s and the mid-2000s (May~next April), it was shown that there was significant difference between December and January (P<0.05), and there was no significant difference during February~November. In the current state by each region, the average number of common goldeneyes was 48.33; 26.17 in Daema-deung (DMD), 1.50 in Jangja and Sinjaso (JJ and SJD), 82.33 in Saja and Doyo-deung (SJ, DYD), 62.00 in the south end of Ulsukdo (LUD) and 69.67 in Ulsukdo (USD). There was highly significant difference among regions (P<0.01). The common goldeneyes tend to use the upper and lower part of Noksan floodgate of Seonakdonggang (west branch of Nakdonggang) where the flow of water is smoothly, the river is wide and the water is relatively shallow due to extension construction of Noksan floodgate. In addition, as development in the west area of Busan due to construction of a new port and designation as the Free Economic Zone has harmful influences to the local ecosystem in Nakdonggang Estuary, it is under an urgent condition to prepare for the maintainance and preservation the ecosystem in this area.