The　effect　of　saline　on　the　shear　strength　of　compacted　bentonite　is　important　to　investigate　the　safety　assessment　of　engineering　barriers　of　deep　geological　repositories.　Different　methods　used　for　saturating　compacted　specimens　yield　inconsistent　relationships　between　shear　strength　and　salt　solution　concentration.　In　this　study,　we　performed　direct　shear　tests　on　compacted　Na-bentonite　saturated　with　distilled　water　and　Na　solutions　using　the　constant-vertical　stress　(CP)　method　and　the　constant-volume　(CV)　method.　Scanning　electron　microscopy　(SEM)　and　nuclear　magnetic　resonance　(NMR)　measurements　were　conducted　to　investigate　the　microstructural　characteristics　of　compacted　bentonite.　The　results　show　that　the　measured　shear　strength　increases　with　increasing　vertical　stress　or　solution　concentration.　Furthermore,　the　shear　strength　of　specimens　prepared　through　the　CV　method　is　larger　when　distilled　water　is　used　for　saturation;　at　the　same　time,　when　salt　solutions　are　used　for　saturation,　CP　samples　show　greater　shear　strength.　On　the　microscale,　both　SEM　images　and　NMR　results　show　that　specimens　become　increasingly　aggregated　with　increasing　pore-water　salinity　and　that　saline　solution　has　a　greater　effect　on　the　microstructure　of　the　compacted　bentonite　when　using　the　CP　method　for　saturation　because　of　the　change　in　volume　during　saturation.　The　intergranular　stress　equation,　which　considers　physicochemical　effects,　is　introduced　to　theoretically　characterize　the　mechanical　behavior　of　compacted　bentonite.　It　is　found　that　the　relationship　between　intergranular　stress　and　shear　strength　is　unique,　independent　of　the　saturation　method.　In　other　words,　the　salt　solution　concentration　affects　the　microstructure,　thereby　affecting　the　interparticle　stress　of　compacted　bentonite.　©　2024　American　Society　of　Civil　Engineers.