The present Namgang Dam had been completed in 2000, Salix subfragilis communities began to form in 2003 and their distribution area have been rapidly extended into nine times in 2010. In order to deduce correlation between water level and distribution of Salix subfragilis communities under this background in Namgang-dam reservoir, distribution characteristics and widening direction of Salix subfragilis communities have been analyzed by aerial photographs and water levels has been reviewed, also heights and ages of Salix subfragilis have been surveyed in field. The water levels of Namgang-dam related germination of Salix subfragilis have been analyzed in May and June from 2000 to 2010, mean water level, minimum water level and maximum water level were 37.87m, 36.99m and 38.82m, respectively. The oldest ages were 9-13 years, average diameters of breast height, average heights, average numbers and average crown area were respectively 3.9-8.8cm, 3.8-7.5m, $0.53/m^2$ and $0.98m^2/m^2$ in sites. Therefore, this results showed that the first recruitment of Salix subfragilis was in May 2002 when water levels have been maintained as 38.76-41.31m and the widening of Salix subfragilis communities was in May 2004 and 2005 when mean minimum water levels have been maintained as 38.76-41.31m. Salix subfragilis communities formed climax forest in Namgang-dam shore, this phenomena were different from the succession processes of Salix in rivers appeared landforming by deposition of sediment.