Abstract: Bentonite is widely seen as a potential buffer/backfill materials for deeply buried geological disposal system to isolate high-level radioactive waste (HLRW). The swelling deformation and shear strength of the bentonite in saline solutions are very important to the safety of the HLRW depository. A conceptual model is proposed to explain the influences of osmotic suction on the volume change and shear strength of the bentonite in a quantitative way. A new formula for the effective stress is proposed as incorporating with vertical stress (p) and osmotic suction (π), and . The relationship is expressed using a unique curve in the form of for the bentonite in NaCl solutions. The peak shear strength is expressed using a unique curve according to the Mohr-Coulomb criterion for the bentonite in NaCl solutions.