The　method　of　seismic　vulnerability　appraisal　and　the　effective　stress　FEM　analyzing　theory　for　underground　construction　in　soft　clay　have　been　studied.　By　the　effective　stress　FEM,　combining　the　accumulative　damage　model,　the　liquefaction　probability　of　soft　clay　is　calculated.　The　seismic　vulnerability　grade　is　got　by　estimating　the　liquefaction　hierarchy.　The　pseudo-static　computational　theory　of　underground　structure　is　expatiated.　At　last,　the　pseudo-static　method　has　been　used　to　calculate　the　seismic　risk　probability　of　underground　construction　in　soft　clay.　The　seismic　vulnerability　grade　is　determined　by　estimating　the　seismic　damage　hierarchy　of　underground　structure.