The　ultimate　seismic　capacity　of　underground　structures　should　be　known　to　provide　a　sufficient　seismic　resistance　during　the　seismic　design,　due　to　the　irreparable　and　difficulty　of　reconstruction　after　collapsed.　However,　existing　single-factor　evaluation　methods,　including　inter-story　drift　ratio,　stress,　strain,　etc.,　only　present　the　serviceability　seismic　capacity　and　cannot　reflect　the　seismic　damage　mechanism　of　underground　structures.　This　paper　proposes　a　performance-based　evaluation　method　to　assess　the　ultimate　seismic　capacity　of　rectangular　underground　structures　by　considering　both　the　characteristics　of　the　structure　itself　and　earthquake　loadings.　Ultimate　horizontal　deformation　capacity　envelope　and　failure　ratio,　derived　from　the　seismic　collapse　mechanism　of　rectangular　underground　structures,　are　the　key　assessment　parameters　of　the　ultimate　seismic　capacity.　Because　the　horizontal　deformation　capacity　of　the　underground　structures　affected　by　the　vertical　loads　was　taken　into　account,　the　obtained　ultimate　seismic　capacity　is　a　band　range　and　expressed　with　the　PGA　of　earthquakes.　The　detailed　procedure　of　the　evaluation　method　is　demonstrated　step　by　step.　Afterwards,　a　case　study　is　presented　to　evaluate　the　ultimate　seismic　capacity　of　Daikai　station　influenced　by　the　spectral　characteristics　and　duration　of　earthquakes.　The　predominant　periods　of　earthquakes　which　the　structure　might　be　sensitive　to　are　discussed.　The　proposed　method　provides　a　detailed　understanding　of　the　performance-based　seismic　evaluation　of　rectangular　underground　structures　and　can　be　extended　to　characterize　other　seismic　performance　levels　of　the　rectangular　underground　structures　in　the　future　work.