The　5　MW　wind　turbine　created　by　National　Renewable　Energy　Laboratory　(NREL)　was　taken　as　the　prototype　in　order　to　analyze　the　dynamic　behavior　of　monopile　supported　offshore　wind　turbines　(OWTs)　excited　by　the　combination　of　wind,　wave　and　earthquake.　Then　parameters　of　the　wave　spectrum　were　determined　by　the　statistical　relationship　between　wind　and　wave　assuming　that　wind　and　earthquake　were　independent　events.　The　FAST　code　was　modified　to　simulate　the　soil-structure　interaction,　and　the　seismic　response　of　OWTs　was　analyzed　by　using　aero-servo-hydro-elastic　coupled　method.　The　running,　park　and　emergency　shutdown　operational　conditions　were　included.　Results　show　that　operational　conditions　significantly　influence　the　deformations　and　internal　forces　of　the　support　structure　of　wind　turbines,　and　the　principles　are　associated　with　the　intensity　of　earthquakes.　The　oscillation　velocity　of　the　blade　is　considerably　influenced　by　earthquakes.　The　amplitudes　of　shear　and　bending　moment　of　critical　section　for　the　support　structure　may　exceed　those　excited　by　extreme　wind-wave　under　the　combined　excitation　of　wind,　wave　and　seismic.　Copyright　©2021　Journal　of　Zhejiang　University　(Engineering　Science).　All　rights　reserved.