Abstract: Dumen dam in Beiliu city breached two times since it has been put into operation in 1968. The first breach occurred in June,1990,when the dam body near the right bank being approximately 20 m long has been destroyed by flood and afterwards reinforced in 1991. On 8th June, 2000, the dam failure occurred adjoining left bank about 25m long. The reasons of dam failure has briefly analyzed in this article, and the rehabilitation for the second breach is introduced as well.