Far-field　harmonic-alike　ground　motions,　in　which　multiple　cycle　pulses　resembled　harmonic　vibrations　were　generated　at　the　later　stage　of　ground　motions,　were　characterized　by　long　duration　and　rich　low　frequency　components.　Its　adverse　influence　on　the　seismic　performance　of　long-period　structures,　such　as　the　isolated　structures,　should　be　revealed　and　validated.　To　this　end,　the　peak　ratio　of　ground　motion　acceleration,　duration　and　response　spectrum　characteristics　of　far-field　harmonic-alike　ground　motions　were　discussed.　Then,　a　single-tower　steel　frame　structure　with　a　large　chassis　was　designed　to　form　three　test　models,　namely　the　aseismic　structure,　base-isolated　structure　and　mid-story　isolated　structure.　One-dimensional　shaking　table　tests　and　numerical　simulations　were　performed　adopting　common　and　far-field　harmonic-alike　ground　motions　as　its　external　excitation　input.　The　impacts　of　long-period　components　and　harmonic-alike　components　on　the　story　drift,　acceleration　and　isolation　layer　deformation　of　these　test　models　were　explored.　Further,　the　vibration　characteristics　of　the　single-tower　isolated　structures　with　horizontal　indentation　size　proportions　of　1　:1.5,　1　:2,　1　:2.5　and　1　:3　were　examined.　The　results　show　that　the　dynamic　responses　of　the　aseismic　and　isolated　structures　when　subjected　to　far-field　harmonic-alike　ground　motions　are　2-3　times　as　large　as　those　when　subjected　to　common　ground　motions,　and　the　seismic-reduction　performance　under　far-field　harmonic-alike　ground　motions　are　not　as　good　as　that　under　common　ground　motions.　The　deformation　of　the　isolation　layer　is　also　enlarged　3-4　times,　which　will　result　in　the　destruction　of　the　isolation　bearing　owing　to　its　excessive　deformation.　Further,　there　is　no　obvious　difference　in　the　vibration　characteristics　of　the　seismic-isolation　structures　with　different　horizontal　indentation　size　proportion.　©　2018,　Editorial　Office　of　Journal　of　Vibration　and　Shock.　All　right　reserved.