A　numerical　framework　was　proposed　for　the　seismic　analysis　of　underground　structures　in　layered　ground　under　inclined　P-SV　waves.　The　free-field　responses　are　first　obtained　using　the　stiffness　matrix　method　based　on　plane-wave　assumptions.　Then,　the　domain　reduction　method　was　employed　to　reproduce　the　wavefield　in　the　numerical　model　of　the　soil-structure　system.　The　proposed　numerical　framework　was　verified　by　providing　comparisons　with　analytical　solutions　for　cases　involving　free-field　responses　of　homogeneous　ground,　layered　ground,　and　pressure-dependent　heterogeneous　ground,　as　well　as　for　an　example　of　a　soil-structure　interaction　simulation.　Compared　with　the　viscous　and　viscous-spring　boundary　methods　adopted　in　previous　studies,　the　proposed　framework　exhibits　the　advantage　of　incorporating　oblique　incident　waves　in　a　nonlinear　heterogeneous　ground.　Numerical　results　show　that　SV-waves　are　more　destructive　to　underground　structures　than　P-waves,　and　the　responses　of　underground　structures　are　significantly　affected　by　the　incident　angles.