With　larger　rotors　and　taller　towers　developed　to　capture　more　wind　energy,　the　tower　structures　become　slenderer　and　more　sensitive　to　wind　loads,　resulting　in　vortex-induced　vibration　(VIV)　in　both　downwind　and　crosswind　directions.　The　vibration　control　is　faced　with　the　challenges　of　broadband　and　multi-directional　dynamic　responses.　Thus,　this　paper　proposed　a　new　type　of　dual-track　nonlinear　energy　sink　(NES)　aimed　to　achieve　the　multi-mode　and　multi-direction　vibration　control　of　wind　turbine　towers.　The　two-degree-freedom　coupled　governing　equations　of　the　wind　turbine　tower　with　the　dual-track　NES　are　established　and　solved　numerically,　with　full　considerations　of　aerodynamics　and　fluid-solid　interactions.　Then,　an　optimized　design　of　the　dual-track　NES　is　performed　theoretically.　To　evaluate　the　vibration　mitigation　performance　of　the　dual-track　NES,　a　series　of　wind　tunnel　tests　are　carried　out　and　analyzed　further,　in　terms　of　the　acceleration　time-history　response,　statistical　characteristics,　frequency　and　damping　ratio.　It　is　demonstrated　that　the　proposed　NES　functioning　as　an　energy-dissipating　device　is　efficient　and　robust　in　mitigating　the　dynamic　response　of　wind　turbine　towers,　even　enabled　to　address　the　vortex　resonance.　It　is　remarkable　that　the　dual-track　NES　can　synchronously　realize　the　vibration　control　in　multi-mode　and　multi-direction　by　increasing　the　damping　ratio　of　primary　structure.