Abstract: The characters of three algalbloom phenomena in Hanjing River in the nineties of 20th century are summarized.The causes and mechanisms of algalbloom occurrence are analyzed from the point of water quality condition,air temperature,hydrological condition.To counter the influences of water pollution control and water quantity distribution of Hanjiang River on algalbloom,the preventing measures are discussed.The conclusions are that administering eutrophication pollution of Hanjiang River as soon as possible is the key to solve the issue and some assistant measures must be taken for decreasing the losing of projects to the minimum,considering the disadvantage influence caused by Three-Gorges and water Transfer Project from Ruth to North (middle route) on water environment of Hanjiang River.