Abstarct: Todays the issues related to the safety and stability of earth dams with hefty fees to have the operation, are of particular importance. Many dams are built with problems caused by seepage, that This seepage may occur from the foundation or dam. Construction of cutoff wall beneath the water structures is the most effective methods for increasing the creepage and reduce the seepage rate. The purpose of this research is to find relationships to influence the location and angle for cutoff wall in foundation of dams. . In this study, using an in lab model of seepage and drainage tank to found The amount of seepage rate and piezometric pressure For a total of 20 different heads and three different lengths of the dam with and one soil with an one cutoff. The results were compared with results of numerical modeling and numerical model showed acceptable fit with the experimental data. seepage and hydraulic gradient of numerical values given in 4000 for a cutoff wall for two cut-off, 4 different depths of cutoff, 7 locations, 11 angle, 4 different heads upstream and downstream of the software was extracted. The results showed that the best place to reduce the seepage rate and hydraulic gradient in the Beginning and end of the dam. that no-dimensional Relation to the effect of depth, angle and location of the cut-off rate of seepage, and hydraulic gradient and creepage were presented. The results showed that creepage of the Line and Blighs theory can be extracted only suitable for laboratory environments and in Below dams Richards and Laplace equations, numerical finite element method of high accuracy. To study the numerical method of measurement software seep/w of the package was used GeoStudio 2007.