This　paper　investigates　the　dynamic　responses　of　offshore　wind　turbine　(OWT)　supported　on　monopile　foundation　in　clay　subjected　to　wind,　wave　and　earthquake　actions.　Based　on　the　open-source　software　platform　OpenSees,　a　three-dimensional　finite　model　of　the　system　is　developed.　The　tower　and　monopile　is　modeled　using　beam　element,　the　pile-soil　interface　behavior　using　nonlinear　Winkler　foundation　approach,　and　the　pile　water　interface　using　hydrodynamic　added　mass.　The　wind,　wave　and　earthquake　actions　are　applied　as　loadings　on　the　system.　The　effects　of　several　parameters,　such　as　wind　velocity,　induction　factor,　wave　period,　peak　ground　acceleration,　and　soil　parameters　on　the　dynamic　responses　of　the　system　are　studied.　The　results　indicate　that　it　is　necessary　to　consider　the　combination　of　wind,　wave　and　earthquake　actions　in　the　design　of　offshore　wind　turbine.