The　integral　abutment　jointless　bridge　(IAJB)　has　many　desirable　characteristics　such　as　long　service　life,　convenient　construction,　and　low　building　and　maintenance　costs.　It　has　thus　been　widely　used　and　applied　both　in　China　and　worldwide.　However,　the　method　to　calculate　the　earth　pressure　of　the　backfill　behind　an　integral　abutment　requires　further　investigation.　Therefore,　considering　an　integral　abutment　bridge　in　China,　a　reciprocating　low-cycle　pseudo-static　test　was　carried　out　to　determine　the　integral　abutment-H-shaped　steel　pile-soil　interaction.　The　mechanical　behavior　and　decaying　law　of　the　earth　pressure　behind　the　abutment　were　evaluated,　and　methods　to　calculate　the　abutment　internal　force　and　earth　pressure　coefficient　were　proposed.　The　results　show　that　a　nonlinear　relationship　exists　between　the　earth　pressure　behind　the　abutment　and　the　loading　displacement　for　the　longitudinal　forward-abutment　direction;　furthermore,　the　earth　pressure　increases　with　the　increase　in　the　loading　displacement　of　the　forward-abutment.　The　earth　pressure　behind　the　abutment　exhibits　primarily　triangular　and　trapezoidal　distributions　along　the　depth　direction.　Meanwhile,　the　position　of　the　resultant　force　for　the　abutment　is　located　at　a　depth　of　two-thirds　the　height　of　abutment.　It　was　also　noted　that　the　earth　pressure　is　exponentially　attenuated　along　the　longitudinal　bridge　and　decreases　to　nearly　zero　at　an　abutment　height　of　two　times　that　behind　the　abutment.　This　means　that　the　longitudinal　movement　of　the　abutment　of　the　IAJB,　under　the　effect　of　temperature,　affects　only　the　backfill　of　the　abutment　within　the　range　of　two　times　the　abutment　height.　The　calculation　shows　that　the　methods　recommended　by　the　specification　are　not　appropriate　for　the　calculation　of　the　earth　pressure　of　the　IAJB.　The　results　obtained　using　the　proposed　method　to　calculate　the　earth　pressure　behind　the　abutment　demonstrate　good　agreement　with　the　test　and　the　bridge　monitoring　results,　and　the　proposed　method　can　thus　be　used　as　a　reference　for　the　design　of　IAJB　and　the　formulation　of　the　specification.　©　2019,　Editorial　Department　of　China　Journal　of　Highway　and　Transport.　All　right　reserved.