Abstarct: Considering the urbanization and population development and the increase in municipal waste production, the design of a healthy and economical landfill for municipal waste is one of the basic needs of human societies. Considering the important issue of land selection, landfill is one of the basic parameters of landfill design. Due to the low permeability of clay, this can be the best choice from the permeability visibility, but due to the significant changes in the effect of Sewage on Clay and reducing the shear strength, and finally reducing the final strength of the desired soil. In this Research, in addition to investigating physical, and chemical tests on soil and water, the effect of Sewage on the shear strength parameters of the landfill site of Shahrood urban society has been investigated. With different experiments (and with different percentages of Sewage), the cohesive and internal friction angle parameters were significantly reduced..