The present study was performed to examine the ecological dynamics of aquatic animal community according to the changes of water environments and biological estimation of water quality by the aquatic animals at Wooyi stream in national park of Mt. Bukhan in June 1992 through June 1993. The values of BOD were 0.2-9.4mg/l range in June 1992, but those improved 0.6-2.2mg/l range in June 1993. The dry weight percentage of substratum particles composed of mostly cobble(64-256mm) at upper region(St.1), but those increased amount of gravel(2-l6mm) and pebble(16-64mm) at middle and down regions (St.2∼St.4). The total taxa numbers of aquatic animals composed of 66 species, 46 genera, 36 families, 16 orders, 7 classes in 4 phyla. In occurrence aquatic animals, consumers of higher trophic level were Moroco oxycephalus in fish and Hynobius leechii in amphibian, consumers of lower trophic level were 64 species of benthic macroinvertebrates. The occurrence species numbers at each site appeared as 21-43 species range and those occurred the most biggest 43 species at upper region(St. 1). The occurrence species numbers according to the survey times were on increased 19 species in June 1992, 26 species in September 1992, 30 species in December 1992, 35 species in March 1993 and 35 species in June 1993. Major dominant species were Nemoura KUa in Plecoptera, Cincticostella castanea and Ecdynonurus kibunensis in Ephemeroptera at upper region(st.1), but those were Chironomus sp. in Diptera, Hirudo nipponica in Annelida and Bakerlymnea viridis in Mollusca at middle and down regions(St.2-St.4). In biological indices, the range of dominance indices decreased from 0.73-0.84 in June 1992 to 0.46-0.73 in June 1993. The range of species diversity indices, extended biotic indices and species richness indices increased from 1.60-2.5, 5-6 and 0.77-1.50 in June 1992 to 1.83-3.06, 7-9 and 1.83-3.06 in June 1993. Therefore, community structure of aquatic animals in this area appeared as more stable condition than that of the one year past. According to the saprobic system based on the species diversity indices of benthic animals, Wooyi stream changed more cleaned water environment conditions α-mesosaprobic area to limnosaprobic area than α-and β-mesosaprobic area of the one year past.