Abstract: There is a large scale of dynam-relaxed rock mass lies in Daliushu dam site. In order to study the destructive mechanism of the rock mass, geological background conditions and earthquake dynamic effects of the region round Daliushu dam site are investigated. The internal relations between earthquake dynamic effects and dynam-relaxed rock mass are confirmed. A further research to the conclusion is given by the dynamic simulation test and dynamic numerical analysis. Consequently once a more serious earthquake happened at present engineering geological conditions, the rock mass of dam site would be further destroyed. That would be threatening to the new constructed water conservancy at Daliushu dam site of Yellow River.