Abstract: The control of tensile force of rubber isolators is critical in high-rise isolated structures. This study proposes a novel tension-adjustable isolator, which is composed of conventional rubber isolator and tension adjustment device (friction damper) connected in series. Under the earthquake, when the tensile force of isolators reaches the preset value, the friction damper starts to slide and provides a friction force which essentially remains constant, thus achieving a basically constant and controllable tensile stress no more than 1 MPa and transmitting it to the rubber isolator. The load-carrying capacity and energy-dissipation capability of the friction damper can to some extent control the vertical displacement of the isolator. To investigate the influence of the building’s aspect ratio on the tensile stress of isolators, two high-rise seismically isolated structures with aspect ratios of 2.2 and 2.7 were designed. The tensile stresses of isolators and seismic responses of structures adopting conventional, uplift, and tension-adjustable isolators were compared and analyzed. The results indicate that the tension-adjustable isolator achieves the expected control target. The excessive tensile stress in the isolated structure using conventional rubber isolators is effectively controlled after adopting the tension-adjustable isolators. The vertical displacement of the tension-adjustable isolators is larger than that of the conventional rubber isolators, but significantly less than that of the uplift isolators, with a reduction ratio up to 48%. The inter-story drift ratio of the structure using tension-adjustable isolators is approximately 6.5% larger than that of the structure using conventional isolators, but smaller than that of the structure adopting uplift isolators. This phenomenon becomes more significant with the increase of the aspect ratio. For the isolation system displacement and absolute floor acceleration, the relative differences of the isolated structures using conventional, uplift and tension-adjustable isolators are within 3%, which can be basically neglected.