The　large　urban　underground　spatial　structures　lead　a　new　trend　of　underground　engineering　development　in　the　future,　whose　seismic　performance　has　been　becoming　a　hot　issue　in　research　of　engineering　and　academic　field.　Based　on　the　calculation　results　of　numerical　simulation　analysis,　a　seismic　risk　assessment　system　was　proposed　which　is　suitable　for　large　underground　spatial　structures.　The　evaluation　indexes　were　built　for　the　first　time　and　the　weight　coefficient　method　was　used　to　determine　the　weight　of　each　evaluation　index.　According　to　actual　application　of　evaluation　project,　the　risk　level　was　described　by　Fuzzy　language,　then　the　seismic　risk　assessment　control　process　for　underground　structure　was　established,　which　is　verified　by　a　project　example.　The　research　result　shows　that:　the　structure　earthquake　damage　mechanism　can　be　directly　present　by　the　seismic　risk　assessment　system　which　was　based　on　numerical　simulation　analysis,　so　the　risk　source　can　be　effectively　traced.　Afterwards,　a　reasonable　level　of　risk　and　corresponding　risk　control　measures　can　be　gotten,　then　the　satisfactory　risk　assessment　result　was　obtained　at　last.　The　establishment　of　earthquake　risk　assessment　system　provides　some　reference　data　for　the　code　of　urban　underground　structures.　©,　2015,　Editorial　Office　of　China　Civil　Engineering　Journal.　All　right　reserved.