A　separated　foundation　model　was　proposed　in　order　to　reduce　the　calculation　scale　of　the　numerical　model　for　analyzing　soil-bridge　structure　dynamics.　The　essence　of　the　wave　input　analysis　model　considering　soil-structure　interaction　was　analyzed.　Based　on　the　large　mass　method,　a　one-dimensional　time-domain　algorithm　of　the　free　field　was　derived.　This　algorithm　could　simulate　the　specified　ground　motion　input　well.　The　displacement　expansion　solution　of　the　free　wave　field　was　solved　based　on　the　propagation　law　of　waves　in　a　medium.　By　separating　the　soil　foundations　around　the　pile　foundations　of　the　bridge,　the　ground　motion　was　transformed　into　an　equivalent　load　applied　on　an　artificial　boundary.　The　separated　foundation　model　could　consider　the　incoherence　effect　and　soil-structure　interaction　simultaneously;　the　number　of　model　elements　were　reduced,　and　the　computational　efficiency　was　improved.　In　order　to　investigate　the　seismic　response　of　a　curved　bridge　considering　soil-structure　interaction　under　spatially　varied　earthquakes,　a　curved　bridge　with　small　radius　was　adopted　in　practical　engineering.　Spatially　correlated　multi-point　ground　motion　time　histories　were　generated,　and　the　nonuniform　ground　motion　field　was　simulated　based　on　the　wave　input　method　on　an　artificial　viscoelastic　boundary.　The　effects　of　different　apparent　wave　velocities,　coherence　values,　and　site　conditions　on　the　seismic　response　of　the　bridge　were　analyzed.　The　results　showed　that　the　spatial　variation　of　seismic　ground　motion　had　a　considerable　effect　on　the　bending　moment　and　the　torsion　of　the　girder.　The　site　effect　had　great　influence　on　the　bending　moment　of　the　pier　bottom.　When　considering　soil-structure　interaction,　the　spatial　variation　of　ground　motion　should　be　fully　considered　to　avoid　underestimating　the　structural　response.　©　2020　by　the　authors.