Abstract: Leachate can have some effect on the mechanical properties of compacted clay liner and subsoil in landfill, although there is not a consistent viewpoint. This paper takes CaCl2 and phenol solutions as the representative of inorganic and organic contaminants in leachate. It conducts compression and strength tests on compacted clay liner with 10% Na-bentonite as addition. With the effect of the two solutions, the soils are of higher compressibility and lower shear strength. Phenol solution results in more remarkable changes in mechanical properties. Its undrained shear strength is 55% of tap water and 0.05molL-1 CaCl2. Under the condition of the same pore ratio, solutions decrease the thickness of diffuse double layer and enlarge the pores, which can be the source of the shear strength reduction. Simulate solutions have an adverse impact on compacted clay liner and subsoil.