In　order　to　investigate　the　change　law　of　natural　soil　shear　properties　of　road　and　bridge　engineering　due　to　the　change　of　the　suction　path　under　repeated　wetting　cycles,　the　unsaturated　triaxial　tests　under　different　confining　pressure,　suction　and　repeated　wetting　cycles　were　carried　out.　Then,　the　knowledge　of　effective　stress　principle,　mineral　composition　and　hysteresis　characteristics　of　soil-water　characteristic　curve　(SWCC)　were　used　to　reveal　and　analyze　the　shear　properties　of　unsaturated　soil　under　different　drying　and　wetting　cycles.　Meanwhile,　the　volume　change　of　unsaturated　soil　after　different　times　of　water　absorption　and　the　influence　of　SWCC　hysteresis　characteristics　on　soil　strength　were　investigated.　And　the　reason　of　the　shear　strength　of　the　soil　was　analyzed　in　depth.　Results　show　that　ductile　behavior　and　shear　shrinkage　behavior　of　natural　residual　soil　under　drying　path　are　similar　to　the　normal　consolidated　soil,　while　brittle　and　shear　dilatancy　characteristics　of　natural　residual　soil　under　wetting　path　are　consistent　with　the　over　consolidated　soil.　The　difference　value　of　shear　strength　between　drying　path　and　wetting　path　doesn＇t　increase　with　the　increase　of　effective　stress　under　the　same　suction　conditions,　but　the　shear　strength　difference　value　between　drying　path　and　wetting　path　decreases　with　the　suction　increase　under　the　same　confining　pressure.　And　the　increase　bulk　volume　of　residual　soil　has　a　characteristics　of　irreversibility　and　hysteresis　since　times　of　absorbing　water,　the　swelling　and　shear　failure　properties　of　soil　is　associated　with　the　level　of　effective　stress　and　suction,　the　larger　the　stress　level　has,　the　more　obvious　of　the　soil　strain-softening　will　be.　Moreover,　the　change　of　soil　saturation　caused　by　the　hydraulic　hysteresis　characteristics　is　related　with　irreversible　deformation　(or　accumulation　of　irreversible　deformation),　and　the　main　reason　for　decline　in　soil　strength　is　the　accumulation　of　irreversible　deformation.　Results　are　of　great　importance　in　the　stability　analysis,　evaluation　and　regulating　design　of　the　residual　slope.　©　2017,　Editorial　Department　of　China　Journal　of　Highway　and　Transport.　All　right　reserved.