The present study was carried out to examine the variations of aquatic animals after the rest year (1992. 6∼1994. 12) in Ui Creek from June, 1992 to March, 1995. The aquatic animals were composed of 104 species, 72 genera, 51 families, 10 orders, 8 classes in 5 phyla in Ui creek. The animals was 57 species in the first survey year, 73 in the second, and 74 in the third. The Ephemeroptera increased from 10 species in the first year to 15 in the third. The Trichoptera increased from 9 species to 13∼14 and the Plecoptera from 4 species to 7. The species number of aquatic animals occurring in the clean waters seems to increase on the duration of rest year. Although the aquatic animals in Ui Creek has been endangered by vegetation shortage, water volume shortage, human interference, and water pollution, aquatic animal diversity since the rest year increased. Therefore, Ui creek ecosystem was considerably recovered by induction of rest year system.