Long-span　cable-stayed　bridges　often　have　a　design　service　life　of　more　than　a　hundred　years,　during　which　they　may　experience　multiple　earthquake　events　and　accumulate　seismic　damage　if　they　are　located　in　seismic-prone　regions.　Earthquake　occurrence　is　discretely　and　randomly　distributed　over　the　life　cycle　of　a　long-span　cable-stayed　bridge　and　often　causes　sudden　drops　in　the　structural　performance　instead　of　yearly　fixed　seismic　performance　degradation.　This　study　thus　proposes　a　digital　twin-based　life-cycle　seismic　performance　assessment　method　for　long-span　cable-stayed　bridges.　The　major　components　of　this　method　include:　(1)　a　seismic　hazard　analysis-based　generation　method　of　earthquake　occurrence　sequence;　(2)　a　digital　twin-based　structural　response　prediction　method　considering　lifetime　earthquake　occurrence　and　sequence;　and　(3)　a　service　life　quantification　method.　The　proposed　method　is　applied　to　a　scaled　long-span　cable-stayed　bridge　with　a　series　of　shake　table　tests.　The　results　show　that　the　digital　twin　can　closely　reproduce　the　life-cycle　seismic　response　of　the　bridge　under　sequential　earthquakes.　The　proposed　assessment　method　provides　a　more　intuitive　presentation　of　the　life-cycle　seismic　damage　accumulation　process　and　a　more　accurate　estimation　of　the　service　life　of　a　long-span　cable-stayed　bridge.