Slurry trench cutoff walls, constructed using self-hardening cement-bentonite (SCB) are the most common form of in-ground vertical contaminant barrier in the world, and are increasingly being used in China. As a kind of vertical anti-seepage wall material， SCB slurry is requently used for the containment of contaminated groundwater and other envirofunental Protection Projeets abroad. Domestie applieation of cement-bentonite slurry walls is not extensive. The objective of this study was to evaluate the effect of water-cement ratio and cement content on the hydraulic behavior of SCB and soil–bentonite (SB) mixtures permeated with water. The experimental program included unconfined compression tests, expansion ratio tests and hydraulic conductivity tests. The test results indicated changes in hydraulic conductivity take place due to the variation of the water-cement ratio and permeant fluid. Cement is a main material in effecting the CSB strength of unconfined compression. Cement greatly influenced the CSB permeability coefficient. Addition of Portland cement to the SB mixtures increased their hydraulic conductivity when permeated with water. The hydraulic conductivity of the SCB specimens permeated with water was inversely related to the cement content.