This　paper　aims　at　influence　of　relative　density　on　deformation　and　failure　characteristics　for　a　shield　tunnel　in　sandy　cobble　strata.　A　series　of　model　tests　were　performed　for　tunnels　with　different　relative　densities　of　0.35,　0.55,　and　0.75.　The　evolution　law　of　the　stratum　deformation　during　the　instability　process　of　the　tunnel　face　was　analyzed.　The　soil　disturbance　range　of　tunnel　face　instability　with　different　relative　densities　was　explored.　The　results　show　that　relative　density　has　a　significant　impact　on　the　extent　of　surface　subsidence.　The　stratum　deformation　caused　by　the　instability　of　tunnel　face　in　the　medium　dense　and　dense　sandy　cobble　strata　only　occurs　significantly　behind　the　tunnel　face,　while　the　stratum　with　loose　sandy　cobble　has　sig-nificant　stratum　deformation　behind　and　in　front　of　the　tunnel　face.　The　method　of　improving　the　relative　density　can　be　used　to　reduce　the　deformation　of　the　sandy　cobble　strata.