Abstract：As a rule，it is prior for large-scale projects to avoid strong earthquake areas. Thus there are little researches on the failure condition of rock mass in strong earthquake areas. The Daliushu dam is locates in the VIII potential seismic region，where the rock mass has been damaged by earthquake many times in history. Different from the general rock mass，it is characterized by dynamo-relaxed rock mass. Rock mass elastic wave velocity is the synthesized reflection of rock quality，rock mass structure，and rock mass existing environment. Quantities of in-situ wave velocity tests have been carried out at the site of Daliushu dam，among which cave wall wave velocity tests on 261 segments，in-between caves rock mass penetrating wave velocity tests on 65 fans，and in-between caves rock mass CT penetrating wave velocity tests on 6 sections. Compared with other dam sites，it is found that the wave velocity of rock mass at the site of Daliushu dam is obviously low，and it is generally equivalent to the wave velocity of weathered strip and faultage of other dam sites. What¢s more，its cave wall wave velocity，the in-between caves rock mass penetrating wave velocity，and the in-between caves rock mass CT penetrating wave velocity have no distinctive difference，which is the specific characteristic of dynamo-relaxed rock mass. Comparison between rock mass elastic wave velocity and rock mass basic quality evaluation BQ shows that there¢s a good linear relation between them. The wave velocity reflects the rock mass quality in the tested area.
