The　integral　abutment　jointless　bridge　(IAJB)　has　been　widely　applied　in　bridge　engineering　for　its　advantages　such　as　long　service　life,　good　integrity,　and　low　maintenance　cost.　However,　its　mechanical　characteristics　and　deformation　law　under　earthquake　loads　lack　thorough　investigations.　In　this　study,　a　practical　engineering　of　IAJB　was　adopted　as　a　sample,　and　an　abutment-steel　H-pile　structural　model　was　manufactured　to　conduct　on　the　seismic　performance　of　integral　abutment-steel　H-pile-soil　system　under　cycle　quasi-static　test.　Some　significant　results　were　obtained,　including　the　failure　mode,　hysteretic　behavior,　skeleton　curve,　horizontal　deformation　law,　and　abutment　rotation　angle　law.　The　results　indicate　that　steel　H-pile　carries　a　large　negative　residual　deformation　but　does　not　damage　under　negative　loading.　Behind　and　at　the　bottom　of　the　abutment　and　at　the　top　of　the　pile,　some　large-scale　voids　are　observed.　The　equivalent　damping　ratio　of　the　abutment　and　pile　is　about　0.35,　which　indicates　a　good　energy　dissipation　capacity.　Furthermore,　the　elastic　bending　stiffness　of　the　specimen　under　positive　loading　is　12.6　times　that　under　negative　loading,　and　the　maximum　bearing　capacity　is　3.85　times　that　under　negative　loading.　Additionally,　the　backfill　has　a　significant　influence　on　the　stiffness　and　bearing　capacity　of　the　specimen.　After　the　test,　the　stiffness　of　the　specimen　reduced　by　33%,　which　is　relatively　unremarkable.　Compared　to　the　displacement　ductility　and　secant　stiffness,　the　loop　stiffness　is　more　appropriate　for　analyzing　the　seismic　performance　of　the　specimen,　and　the　improved　secant　stiffness　can　more　accurately　reflect　the　stiffness　degradation　of　the　specimen.　Considering　the　effect　of　full　and　local　accumulative　deformation,　under　the　large　displacement　load,　the　steel　H-pile　appears　to　have　a　larger　negative,　full　accumulative　deformation,　and　there　are　many　local　accumulative　deformations　along　the　depth　direction.　During　the　loading　process,　the　abutment　only　exhibits　rigid　body　displacement,　and　the　positive　angle　gradually　increases.　Moreover,　the　negative　angle　of　abutment　increases　and　decreases　before　finally　turning　to　the　positive　angle.　These　results　show　that　the　integral　abutment-steel　H-pile-soil　system　exhibits　excellent　seismic　performance.　©　2020,　Editorial　Department　of　China　Journal　of　Highway　and　Transport.　All　right　reserved.