The　dynamic　response　of　underground　structures　is　significantly　influenced　by　the　uncertainties　in　soil　and　structural　parameters,　which　cannot　be　neglected　in　seismic　analysis.　This　study　proposes　an　improved　interval　analysis　method　based　on　Chebyshev　series　theory　to　evaluate　the　uncertainties　in　the　dynamic　response　of　underground　structures.　The　method　predicts　the　extreme　range　of　system　responses　by　determining　the　upper　and　lower　bounds　of　uncertain　parameters.　Unlike　existing　interval　analysis　methods,　the　proposed　approach　is　specifically　extended　and　applied　to　the　dynamics　of　underground　structures.　Additionally,　by　incorporating　the　equivalent　linearization　analysis　method,　the　nonlinear　behavior　of　soil　is　approximately　simulated,　and　the　impact　of　uncertain　soil　shear　wave　velocity　on　the　dynamic　response　of　structures　is　investigated.　Furthermore,　numerical　studies　are　conducted,　and　the　results　are　compared　with　those　from　the　Monte　Carlo　Simulation　(MCS)　method　to　validate　the　applicability　and　effectiveness　of　the　proposed　method.　The　findings　indicate　that　the　method　accurately　captures　the　upper　and　lower　bounds　of　the　dynamic　response　of　the　site　and　underground　structures,　with　significantly　higher　computational　efficiency　than　the　MCS　method,　demonstrating　its　strong　engineering　practicality.　Specifically,　when　using　a　third-　or　fourth-order　Chebyshev　series　expansion,　the　results　align　closely　with　the　MCS　method.　Moreover,　the　proposed　method　reduces　computational　time.　It　extends　the　application　of　the　Chebyshev　series　in　uncertainty　analysis,　providing　an　efficient　and　reliable　tool　for　addressing　uncertainty　problems　in　underground　structures.　©　2025　The　Authors