Granite　in　underground　water-sealed　storage　caverns　has　usually　been　immersed　for　a　long　time.　The　immersion　affects　the　mechanical　properties　and　failure　mechanism　of　granite　with　maximum　free　water　absorption;　therefore,　it　is　crucial　to　study　the　behavior　of　granite　under　different　confining　pressures　for　engineering　construction.　A　triaxial　compression　test　with　maximum　free　water　absorption　was　conducted　on　granite　and　its　mechanical　properties　were　analyzed.　A　fracture　scanning　electron　microscope　test　was　carried　out　to　analyze　the　microstructural　characteristics　and　reveal　the　failure　mechanism.　The　test　results　showed　that　the　differential　stress-axial　strain　curve　can　be　divided　into　the　initial　compaction　stage,　the　elastic　deformation　stage,　the　plastic　deformation　stage,　and　the　post-peak　strain-softening　stage.　With　an　increase　in　confining　pressure,　the　duration　of　the　initial　compaction　stage　decreased,　while　the　plastic　deformation　stage　and　the　peak　strength　and　peak　strain　stages　increased.　For　the　confining　pressure　range　of　0-20　MPa,　the　peak　stress　difference　of　granite　with　maximum　free　water　absorption　was　between　146.0　and　307.6　MPa.　The　elastic　modulus　was　between　31.36　and　44.18　GPa.　The　cohesion　(c)　of　the　rock　sample　studied　was　26.84　MPa　and　the　internal　friction　angle　(phi)　was　51　degrees.　The　failure　mechanism　of　granite　is　tensile-shear　composite　failure,　predominantly　with　tensile　failure　under　low　confining　pressure　regimes,　and　the　inclined　fracture　surface　is　mainly　due　to　shear　failure　under　high　confining　pressure　conditions.　These　research　results　provide　updated　reference　data　for　rock　engineering　involving　granitic　mechanical　properties　and　failure　mechanisms　in　submerged　caverns.