The fill placement works on the dam foundation as overburden loading. This loading would influence the stress states in the foundation resulting in the change of strain and permeability in the underground. Therefore, the authors actually measured the deformation of dam foundation and the change of permeability due to the fill placement at two damsites. The results measured at both damsites indicate that the fill placement causes the compression of dam foundations accompanying the decrease of permeability. The authors feel that these results are very helpful for the determination of effective grouting design for the foundation of filldams. Furthermore, the authors theoretically try to explain the relationship between the compressive strain of the foundations and the decrease of permeability due to the fill placement by using the simple models.