A　series　of　large-scale　shaking　table　tests　were　performed　to　investigate　the　seismic　response　of　an　underground　subway　structure　with　irregular　sections　in　adverse　soil　conditions　(soft　and　liquefiable　sites).　Emphasis　is　placed　on　the　influence　of　the　adverse　soil　conditions　on　the　response　of　the　irregular　underground　structures　and　over　areas　of　soil-structure　interface,　involving　buildup　of　pore　pressures　and　resulting　large　deformations.　The　results　indicate　that　the　seismic　responses　of　the　structure　and　the　soil　were　sensitive　to　input　motions　with　richer　low-frequency　components.　The　seismic　damage　of　the　underground　structure　was　more　significant　in　the　soft　site　as　compared　with　that　in　the　liquefiable　site.　The　liquefiable　site　worked　as　a　natural　seismic　isolation　system　for　the　underground　structure,　significantly　reducing　the　damage　potential　to　the　model　structure.　Under　the　action　of　a　strong　earthquake,　the　horizontal　displacement　response　of　the　liquefiable　site　sharply　increased　compared　with　that　of　the　soft　site.　With　respect　to　the　structure　response,　the　interlayer　displacement　of　the　structure　in　the　soft　site　was　approximately　twice　that　in　the　liquefiable　site.　The　lateral　deformation　of　the　structure　was　greater　in　the　soft　site　and　the　interior　structure　column　was　more　prone　to　damage.　Correspondently,　the　peak　and　the　residual　strains　in　the　structural　components　in　the　soft　site　were　higher　than　those　in　the　liquefiable　site　were.　The　results　provided　insights　into　the　site　effects　of　adverse　soil　conditions　on　the　seismic　response　of　underground　structures,　especially　on　the　seismic　damage　process　and　the　failure　mechanisms　of　the　structure　members.