Abstract: Base-isolated structures can effectively reduce seismic effects by elongating their natural periods. Under long-period ground motions, excessive displacement at the isolation layer may occur. Dampers can reduce the displacement of the isolation layer, but excessive damping force will lead to an increase in the acceleration of the superstructure. Vibration-sensitive facilities such as laboratories and data centers, as well as complex working conditions in strong earthquake areas or soft soil sites, put forward more stringent performance requirements for the safety and reliability of seismic isolation systems. Leveraging the unique characteristics of inerter devices, such as apparent mass amplification and dynamic negative stiffness effect, this study proposes an inerter-based synergistic isolation system composed of rubber bearings, elastic sliding bearings and cam inerters to achieve multi-objective control of story drift and floor absolute acceleration. A theoretical model of the proposed system is established, and its effectiveness is validated through shaking table tests. The equations of motion for a multi-degree-of-freedom inerter-based synergistic isolation system are derived, followed by the development of a multi-objective design methodology. A case study is presented to demonstrate the proposed approach, with comparative analysis against conventional combined isolation system. The results indicate that the proposed system achieves effective multi-objective control of key performance indices to meet structural performance requirements. Compared with conventional combined isolation systems, it further enhances structural performance and reliability of isolation layer.