The　rolling　soft　robot　usually　uses　circular　or　ellipse-like　configurations　but　the　factors　influencing　the　robot　configuration　have　not　been　sufficiently　investigated.　This　study　presents　a　theoretical　model　for　investigating　the　morphology　evolution　of　a　thin　elastic　ring　under　gravity.　The　ring　exhibits　an　ellipse-like　morphology　under　gravity,　with　this　morphology　governed　by　the　ratio　of　gravity　to　bending　stiffness.　An　increase　in　the　ratio　of　gravity　to　bending　stiffness　results　in　a　flatter　ellipse-like　structure,　accompanied　by　an　enhanced　contact　length　with　the　ground　and　a　concomitant　reduction　in　its　gravitational　moment　on　the　slope.　The　ellipse-like　structures　calculated　by　the　theory　are　in　good　agreement　with　the　experiment　and　simulation.　This　study　provides　a　theoretical　basis　for　the　material　selection　and　geometry　determination　of　the　configuration　design　of　required　rolling　soft　robots.