<p>The energy-saving H-infinity control problem for an improved two-degree-of-freedom (2DOF) vibration isolator is investigated in this study. Firstly, the model of the improved 2DOF active control vibration isolator is presented, and the dynamic equations of the system are established. Subsequently, an energy-saving H-infinity optimal controller based on output feedback is designed for the improved 2DOF active control vibration isolator model, resulting in an output control force with energy-saving effects. The novel controller is characterized by the replacement of a portion of the active control force with the negative stiffness mechanism, thereby reducing the overall active control force under optimal conditions. To validate the energy-saving effects of the new controller, numerical simulations are conducted under three types of inputs. The results indicate significant energy-saving effects, with the root mean square (RMS) values of the actuator output force reduced by 57.14%, 92.67%, and 90.82%, respectively. Further numerical simulations are performed considering actuator time delays. Under the same three excitation inputs, the improved vibration isolator is shown to outperform the original isolator in terms of vibration isolation performance, while also demonstrating greater energy-saving capabilities, with reductions of 54.28%, 87.22%, and 4.03%, respectively.</p>