The　serious　attention　on　anti-seismic　design　of　underground　structures　has　been　paid　after　the　collapse　of　the　Daikai　subway　station　in　the　Great　Hanshin　earthquake　in　1995.　Great　efforts　have　been　made　in　investigating　the　failure　mode　and　the　collapse　mechanism　of　the　station　structure　based　on　theoretical,　numerical　and　experimental　approaches.　However,　a　consensus　on　the　failure　mode　and　the　collapse　mechanism　hasn＇t　been　achieved　yet.　In　this　paper,　a　three-dimension　numerical　model　of　nonlinear　earthquake　response　simulation　of　the　station　structure　was　firstly　established.　Then,　the　failure　mode　and　the　collapse　mechanism　of　the　underground　structure　were　systematically　explored　from　seismic　action　mode,　different　load　bearing　functions　of　structural　components,　incompatibility　of　deformation　capacity　between　intermediate　columns　and　lateral　walls　during　earthquake.　Further,　a　concept　of　key　supporting　columns　for　anti-seismic　design　of　underground　structures　was　presented.　©　2017,　Editorial　Office　of　China　Civil　Engineering　Journal.　All　right　reserved.