Monopile　offshore　wind　turbines　(MOWT)　are　inserted　into　sea　water　and　sea　bed　soil.　As　the　piles　are　usually　embedded　into　the　soil　as　deep　as　about　40　m,　dynamic　pile-water　and　pile-soil　interactions,　as　well　as　seismic　excitation　non-uniformity,　often　occur　under　earthquake.　In　this　paper,　the　response　spectrum　method　(RSM)　is　developed　to　calculate　the　maximum　response　of　MOWT　considering　the　pile-water　and　pile-soil　interactions　subjected　to　the　non-uniform　seismic　excitation.　The　tower　and　pile　are　modeled　by　Timoshenko　beam　elements,　with　both　nacelle　and　rotor　including　hub　and　blades　integrated　as　a　lumped　mass　at　the　top　of　the　tower.　The　pile-water　and　pile-soil　interactions　are　considered　by　added　mass　and　soil　spring　at　their　interfaces,　respectively.　The　non-uniform　seismic　excitation　is　obtained　by　the　site　transfer　function　from　the　horizontal　earthquake　motions　or　design　response　spectrum　at　the　water-soil　interface.　The　seismic　analysis　model　is　solved　by　using　a　multiple-support　RSM　under　design　response　spectrum.　Seismic　responses　of　a　case　of　5-MW　MOWT　on　two　types　of　soil　sites　are　analyzed.　The　results　indicate　that　the　pile-water　and　pile-soil　interactions　and　seismic　excitation　non-uniformity　should　be　considered　in　analyzing　such　seismic　problems　of　MOWT,　while　the　RSM　can　be　an　effective　tool.