The　triaxial　equipment　of　GDS　is　improved　based　on　the　digital　image　processing　technique,　and　the　failure　process　and　shear　band　mode　of　medium　sand　under　different　stress　paths　are　studied.　Thirteen　monotonic　shearing　tests　are　performed,　including　isotropic　stress　consolidation　and　anisotropic　stress　consolidation.　Deformation　characters　and　strain　fields　of　sample　surface　at　different　time　during　triaxial　compression　progress　are　recorded,　and　the　failure　progress　of　samples　is　presented.　The　results　show　that,　under　different　stress　paths,　the　failure　progress　of　samples　is　closely　related　to　the　stress　path.　Different　realizing　ways　of　increasing　pore　pressure　and　decreasing　the　total　stress　for　the　same　stress　path　may　lead　to　different　results.　The　final　failure　mode　can　be　divided　into　three　kinds,　namely　uniform　bulging,　single　shear　band　and　cross　shear　band.　The　effective　stress　ratio　regularity　shows　that　the　higher　stress　ratio　of　consolidation,　the　lower　value　of　effective　stress　ratio　and　the　bigger　value　of　reduction　after　peak　value.　The　failure　mode　is　initially　determined　before　the　peak　value　of　effective　stress　ratio,　macro　stability　is　reached　after　the　peak　value.