Satisfactory　performance　of　offshore　wind　turbines　is　governed　by　the　cyclic　response　of　its　foundation　under　wind　and　wave.　Most　methods　of　evaluating　the　lateral　cumulative　deformation　of　monopile　due　to　cyclic　loading　are　based　on　small-diameter　pile　tests　installed　in　dry　sand.　This　paper　investigates　the　cumulative　deformation　of　large-diameter　monopiles　installed　in　saturated　sand.　A　numerical　model　was　developed　employing　FLAC3D　and　was　validated　by　comparing　its　predictions　with　the　results　of　triaxial　tests　and　centrifuge　tests.　The　validated　numerical　model　was　used　to　evaluate　and　compare　the　cyclic　responses　of　monopiles　between　saturated　case　and　no　pore　pressure　case.　To　evaluate　the　cumulative　deformation　for　offshore　monopile　due　to　cyclic　loading,　the　numerical　model　was　refined　to　account　for　the　effects　of　number　and　amplitude　and　frequency　of　cyclic　loading,　soil　permeability　coefficient,　soil　relative　density　and　pile　diameter.　It　was　found　that　the　larger　subsidence　and　the　less　capacity　of　soil　around　the　pile　is　caused　by　accumulation　and　dissipation　of　transient　excess　pore　pressure,　thus　the　monopile　in　saturated　sand　would　experience　the　larger　cumulative　deformation.　Correspondingly,　based　on　this　parametric　study,　an　analytical　model　was　developed　to　calculate　the　pile-top　cumulative　displacement　of　offshore　large-diameter　monopile　under　lateral　cyclic　loading　considering　the　effects　of　pile　diameter.　This　analytical　model　was　validated　against　the　results　of　centrifuge　tests　and　model　pile　tests　in　saturated　sands.