This　study　aims　to　propose　a　fragility　analysis　method　for　evaluating　the　longitudinal　seismic　performance　of　long-line　utility　tunnels　based　on　nonlinear　incremental　dynamic　analysis　(IDA).　To　this　end,　a　simplified　beam-spring　model　is　established,　to　reasonably　consider　the　mechanical　properties　of　the　joint　and　the　soil-tunnel　interaction.　A　series　of　17　sets　of　ground　motion　records　are　selected　and　uniformly　scaled　to　different　intensity　levels　as　the　input　of　one-dimension　free　filed　analyses　to　obtain　the　ground　motions　at　the　bottom　slab　of　a　utility　tunnel.　Finally,　the　seismic　analysis　of　the　utility　tunnel　considering　wave　passage　effects　is　conducted.　Based　on　the　IDA　results,　the　optimal　intensity　measure　is　selected.　With　the　damage　measure　of　the　peak　joint　opening,　the　fragility　curves　of　the　utility　tunnel　are　established　using　the　peak　velocity　at　the　bottom　slab　of　the　tunnel　and　the　peak　velocity　at　the　ground　surface　as　the　intensity　measures,　respectively.　The　failure　probability　of　the　utility　tunnel　under　different　earthquake　intensity　levels　is　also　obtained.　The　proposed　fragility　curves　and　failure　probability　of　the　utility　tunnel　in　typical　site　II　can　provide　an　effective　tool　to　estimate　the　seismic　performance　of　this　type　of　underground　structures　and　a　reliable　basis　for　predicting　damage　under　different　earthquake　intensity　levels.　©　2024　Chinese　Society　of　Civil　Engineering.　All　rights　reserved.