We investigated monthly variation of the fish community and abundance at stream of Mt. Chi-ak from May to November 1993. Total number of species of collected fishes were twenty-six species belonging to eight families. Twelve species of them were found te be endemic species of Korea. In this study, Cottus poecilopus and Moroco kumgangensis are confirmed abundantly inhabitant at the stream of Mt. Chi-ak. Dominant species were Cottus poecilopus, Moroco oxcephalus at the station 1, Zacco temmincki, Coreleuciscus splendidus at the station 2,3,4, and Zacco platprus, Zacco temmincki at the station 5. Rare species were Lampetra reissneri, Opsariichthys bidens, Squalidus gracilis, Silurua microdorsalis, Hemibarbus mylodon, Leiocassis ussuriensis, Acheilognathus signifer. When the water level rises, Moroco kumgangensis and Cottus poecilopus migrate from station 1 to station 2. On the other hand when the water temperature increase, Liobagrus andersoni, Cobitis rotundicaudata, Coreoperca herzi and coreleuciscus splendidus are migrate from station 2 to station 1. Estimated abundance and biomass of fish were 716ind./100m^2 and 55.4g/m^2 at St. 1,986 ind./100m^2 and 68.92g/m^2 at St.2, 1,485 ind./100m^2 and 98.15g/m^2 at St.3 and 1,304 ind./100m^2 and 61.63g/m^2 at St.4, 1,406 ind./100m^2 and 74.61g/m^2 at St. 5.