Two　types　of　nonlinearities　including　geometric　and　material　are　most　commonly　encountered　in　structural　analysis.　In　the　previous　research,　the　nonlinear　of　the　soil　and　tower　material　has　been　widely　considered　in　the　dynamic　and　static　analyses　of　offshore　wind　turbine.　However,　geometrical　nonlinearity　is　also　very　important　for　the　cantilever　structures　with　large　deflection　under　tip　concentrated　vertical　load.　This　study　investigates　the　effect　of　the　geometrical　nonlinearity　on　the　responses　of　offshore　wind　turbine　supported　on　monopile　foundation　in　clay　subjected　to　the　external　vibration　sources.　A　finite　element　model　of　the　system　is　developed　using　software　ABAQUS.　Tower　and　monopile　is　modeled　using　beam　elements　with　ideal　elastic-plastic　material,　pile-soil　interaction　is　modeled　using　nonlinear　spring　elements　and　pile-water　interaction　is　replaced　by　using　added　mass.　Pushover　analysis　of　the　system　and　dynamic　analysis　of　the　system　subjected　to　wind,　wave　or　earthquake　loads　are　performed　in　the　present　study.　It　is　found　that　the　geometrical　nonlinearity　should　be　considered　in　the　design　of　offshore　wind　turbine.　©　13th　International　Conference　on　Shock　and　Impact　Loads　on　Structures,　SILOS　2019.　All　Rights　Reserved.