In order to analysis of the water pollution of the Anyang stream(one of the biggest branch streams of the Han River) and its main tributaries, the geological and topographical and rainfall features in its basin were investigated. To do this, the water samples were collected 23 points of the upper, mid and down of Anyang stream and its tributaries and were analyzed based on the chemical methods, Korean Biotic Index(KBI) and Saprobien systems. The Anyang stream basin has a characteristic of topographical torrential heavy rainfall like a typical rainfall feature in Korea. The concentration and the outflow rate of rainfall is very different in seasonal, and water pollution in dry season is especially severe. After 1997, although the water quality status of stream has been improved gradually, the concentration of T-N and SS at the upstream is increased due to the deficiency of facility used for collecting wastewater released from industrial factories, livestock farms and residential areas. The mainstream of the Anyang stream is classified into the 5th grade water as polysaprobic water area according to Saprobien system and the biotic index is over 2.5 in overall. Most of tributaries have 1~3 grade water limit with ${alpha}$- and ${eta}$-mesosaprobic except the upper and mid streams of Samsung tributary, in which pollution status is the lowest part. Though Sambong tributary is ${alpha}$-mesosaproboic, biotic index is low because of the appearance of abundant benthos animals in farming and fishing villages.