Offshore　wind　turbine　structure　is　the　dynamic　sensitivity　structure.　The　structure　will　long　be　hit　by　wave　and　wind　loads,　hence　the　frequency　of　the　structure　may　be　varied.　When　the　natural　frequency　of　offshore　wind　turbines　is　closed　to　the　frequency　of　wave　or　wind　loads,　it　enlarges　the　dynamic　response　of　the　structure　and　reduces　the　overall　stability　of　wind　power　structure.　In　this　paper,　based　on　OpenSees　finite　element　platform,　the　Boulanger　model　is　employed　to　simulate　the　pile-　soil　interaction,　then　the　frequency　model　of　offshore　monopile　foundation　is　established.　Taking　the　large　diameter　steel　piles　into　account,　the　influence　of　the　added　water　mass　on　natural　frequency　of　large　diameter　steel　piles　is　studied.　The　results　show　that　the　added　water　mass　has　great　influence　on　the　natural　frequency　of　large　diameter　steel　piles.　Based　on　the　foregoing,the　impact　laws　of　pile,soil　and　sea　water　on　the　natural　frequency　of　the　offshore　foundation　are　further　analyzed.　Using　the　concept　of　the　frequency　variation　rate,the　natural　frequency　sensitivity　of　different　foundations　and　different　diameters　single　pile　foundations　are　discussed.　©　2020,　Solar　Energy　Periodical　Office　Co.,　Ltd.　All　right　reserved.