Retaining　walls　with　relief　shelves　(RS-RW)　show　great　potential　for　enhancing　the　stability　of　supporting　structures　under　seismic　impact.　However,　conventional　analysis　methods　may　not　be　accurate　due　to　the　presumptive　damage　modes.　In　this　paper,　the　seismic　slip-line　method　(SSLM)　was　implemented　to　study　the　active　damage　mode　of　the　fill　behind　unloaded　retaining　walls　under　seismic　action,　which　was　validated　by　comparison　with　the　finite　element　limit　analysis.　The　study　found　that,　under　the　base　rotation　(RB)　mode　of　RS-RW,　the　seismic　active　earth　pressure　(ES)　increased　by　over　33%　as　the　seismic　horizontal　acceleration　rose　from　0　to　0.1　g.　Furthermore,　it　was　determined　that　the　stability　of　the　retaining　structure　in　seismic-prone　areas　could　be　significantly　enhanced　by　incorporating　a　relief　shelf　with　a　length　approximately　0.4　times　the　wall　height　(H)　and　positioning　it　at　a　depth　of　0.3-0.4　H　from　the　top　of　the　wall.　These　results　demonstrate　that　the　SSLM　can　effectively　resolve　the　stress　state　at　every　point　within　the　fill　behind　the　retaining　wall,　aiding　in　the　comprehensive　analysis　of　the　overall　plastic　failure　mechanism.