A　new　visual　model　was　used　to　study　the　failure　mechanism　and　earth　pressure　of　cohesionless　narrow　backfill　installed　behind　a　rigid　retaining　wall.　The　experimental　system　can　simulate　the　different　displacement　modes　of　the　retaining　wall,　inclinations　of　the　retaining　wall　and　widths　of　the　backfill.　Using　a　HD　camera,　displacement　transducers　and　earth　pressure　cells,　the　deformation　of　the　backfill,　displacement　of　the　retaining　wall　and　earth　pressure　on　the　wall　were　recorded.　Image　data　were　post-processed　using　geo-particle　image　velocimetry.　The　shear　strain　contours　and　displacement　vector　diagrams　of　the　soil　were　obtained.　The　test　results　showed　that　under　the　translation　mode　of　the　retaining　wall,　a　sliding　surface　develops　as　a　reflection　between　the　walls　to　reach　the　ground.　As　the　backfill　width　decreases,　the　number　of　reflective　sliding　surfaces　increases.　The　active　earth　pressure　on　the　wall　is　less　than　that　obtained　from　calculations　performed　using　classical　theories　and　has　a　nonlinear　distribution.　The　number　of　reflective　sliding　surfaces　can　be　reduced　by　increasing　the　retaining　wall　inclination.　When　the　retaining　wall　was　under　a　rotation　displacement　mode,　the　backfill　exhibited　progressive　failure,　and　no　reflective　sliding　surface　was　produced.　The　tests　help　to　understand　the　special　failure　mechanism　and　earth　pressure　distribution　of　narrow　backfills　and　provide　a　basis　for　theoretical　research.　©　2022,　The　Author(s),　under　exclusive　licence　to　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature.