Seismic　response　and　vulnerability　of　subway　station　underground　structures　are　greatly　influenced　by　kinematic　soil-structure　interaction,　which　is　a　function　of　soil　properties　and　stiffness.　Therefore,　this　paper　investigates　the　influence　of　parameters　associated　with　soil-to-structure　relative　stiffness　(F)　on　the　seismic　fragility　curves　of　underground　structures.　Incremental　dynamic　analysis　method　is　conducted　employing　finite　element　analysis　to　establish　the　fragility　curves　of　the　station　structure　considering　44　earthquake　records.　The　soil　was　simulated　as　a　two-dimensional　(2D)　finite　element　domain　and　its　nonlinear　behavior　is　described　employing　the　Davidenkov　constitutive　model.　Appropriate　plasticity　models　simulated　the　nonlinearity　of　concrete　and　reinforcing　rebars.　It　was　found　that　the　failure　probability　of　the　structure　decreases　significantly　as　soil　shear　wave　velocity　increases,　and　the　change　of　probability　of　structural　failure　was　quantified　for　changes　in　shear　wave　velocity　within　the　range　200　m/s　to　600　m/s.　It　was　also　found　that　the　failure　probability　of　subway　station　in　heterogeneous　soil　is　significantly　higher　than　that　of　a　structure　buried　in　homogeneous　soil.　On　the　other　hand,　the　cross-section　type　of　the　structure　has　less　influence　on　its　seismic　vulnerability.　The　seismic　performance　of　the　structure　with　higher　F　is　relatively　better,　while　there　are　special　cases　where　some　structures　with　high　F　that　are　more　susceptible　to　failure　under　earthquake　than　structures　with　lower　F.　The　findings　can　provide　helpful　guide　for　the　performance-based　seismic　design　of　underground　structures.