The　seismic　response　characteristics　of　underground　structures　are　very　different　from　those　of　aboveground　structures.　Great　efforts　have　been　made　in　investigating　the　influence　factors　on　the　seismic　responses　of　rectangular　underground　structures,　while　the　theoretical　analyses　and　comprehensive　understandings　remain　insufficient　in　the　current　research.　In　order　to　shed　light　on　the　seismic　response　characteristics　of　the　shallow　buried　rectangular　underground　structure,　an　extended　parametric　study,　based　on　a　real　underground　structure,　the　Daikai　subway　station　in　Japan　was　conducted　in　the　present　paper.　In　particular,　a　two-dimensional　soil　structure　system　was　adopted　for　the　dynamic　time-history　analysis.　The　equivalent　linear　model　was　used　to　consider　the　nonlinear　behaviors　of　the　soil　elements,　and　the　elastic　model　was　used　to　simulate　the　structure　elements.　A　variety　of　critical　factors　that　may　significantly　affect　the　seismic　responses,　such　as:　(i)　earthquake　load　condition,　(ii)　structure　inertia　effect,　(iii)　soil　inertia　effect,　(iv)　soil-structure　relative　stiffness,　and　(v)　soil　structure　interface　properties　were　comprehensively　investigated　in　this　study.　The　variations　of　the　horizontal　relative　deformation　between　the　top　and　bottom　slabs　of　the　structure　and　the　internal　forces　of　four　representative　sections　that　were　most　concerned　in　seismic　design　were　calculated　and　compared　in　different　cases,　and　the　soil　pressures　and　shear　forces　around　the　structure　were　also　systematically　discussed.　The　numerical　results　indicated　that　the　seismic　responses　were　obviously　affected　by　the　soil　inertia　effect　and　soil　structure　relative　stiffness,　and　more　attentions　should　be　paid　to　these　critical　factors　during　the　seismic　design　of　the　underground　structure.　The　presented　results　can　lead　to　better　understandings　on　the　seismic　responses　of　the　shallow　buried　rectangular　underground　structure　and　can　provide　some　improvements　to　the　existing　simplified　methods　and　guide　the　seismic　design　of　the　underground　structure.