To　enhance　the　accuracy　and　reliability　of　the　design　calculation　for　reinforced　concrete　slope-stabilizing　pile,　a　three-dimensional　and　threefold　nonlinear　numerical　modeling　method　was　proposed.　Namely,　in　the　three-dimensional　modeling　the　material　nonlinearity　is　considered　with　soil　modeled　with　a　nonlinear　elastic　model,　and　reinforced　concrete　pile　with　an　advanced　damaged　plasticity　model　for　the　first　time　in　particular.　The　boundary　nonlinearity　is　considered　by　using　the　Coulomb　friction　to　model　the　interactions　on　both　soil-pile　and　soil-rock　interfaces.　And　the　geometry　nonlinearity　is　taken　into　account　by　adopting　the　large　deformation　algorithm.　In　addition,　a　post-processing　approach　for　the　sectional　bending　moment　of　pile　body　is　presented　when　a　reinforced　concrete　pile　is　modeled　with　solid　elements,　and　steel　bars　with　truss　elements　embedded　in　concrete.　The　proposed　method　was　successfully　applied　to　model　a　pilot　pile.　The　same　ultimate　bearing　capacity　as　the　test　was　obtained.　Comparisons　also　show　that　the　computed　displacements　and　maximum　moments　agreed　well　with　the　measurements　regardless　of　whether　the　pile　was　working　in　the　elastic　or　damaged　plastic　state,　and　even　the　advent　of　cracking　was　identical　with　the　test.　In　addition,　the　fluctuation　phenomenon　of　moment　diagrams　of　the　pile　body　in　the　damaged　plastic　state　as　well　as　the　spatial　distribution　of　soil　resistance　were　revealed　for　the　first　time.　The　outcomes　highlighted　the　accuracy,　reliability　and　efficiency　of　the　proposed　method.　©　2022,　Korean　Society　of　Civil　Engineers.