Abstract: Because of complex geological conditions and different design standards, some dams are found potential problems and seepage is one of them. The working performance of damfoundation, to a large degree, is controlled by curtain extent and its sealing effect. There are manymethods to appraise anti- seepage effect of curtain- grouting and its time- variance, such as water pressure test, computer tomography, macroscopic and microscopic dynamic analysis of groundwater, evaluation of sludge and so on. This paper discussed these methods and gave comments. At last, the idea that multiple approaches should be adopted in evaluation was advanced.