A new type of vertical seismic isolation device， consisting of hydraulic jack and accumulator （VSI-HJA）， is proposed for vertical vibration isolation of building structures. Firstly， the working principle of VSI-HJA is introduced， and the non-linear stiffness model and the energy dissipation model of the isolation system are established. Secondly， cyclic loading tests were conducted to assess the frequency dependence and displacement amplitude dependence， and the equivalent stiffness and energy dissipating parameters of VSI-HJA were measured. The test results indicate that the vertical stiffness of the device varies nonlinearly with an error within ±3% between the theoretical and experimental values， the seismic isolation device develops a full hysteresis loop， shows strong energy dissipation capacity， has velocity-dependent damping property. The test results are in good agreement with the calculated results. Finally， the effectiveness of the proposed VSI-HJA is further investigated by simulating the seismic isolation effect of structures with different device parameters using the finite element method. The research results reveal that the displacement response of the isolated structure increases correspondingly with the weakening of their vertical stiffness， while the acceleration response decreases. The isolated structure demonstrates excellent seismic isolation performance， and the vertical displacement of the isolated structure under the earthquake can be effectively controlled by the damping adjustment.