Based　on　empirical　genetic-simplex　algorithm　(EGSA),　an　analytical　method　of　the　interior　stability　of　soil-nailed　structure　for　deep　foundation　pits　was　proposed.　Compared　with　genetic　algorithm　(GA),　it　was　shown　that　EGSA　was　better　than　GA.　The　calculation　of　the　integral　stability　of　a　practical　engineering　example　was　carried　out　by　using　the　proposed　method　and　commercial　software　respectively.　It　was　shown　that　the　most　dangerous　sliding-plane　could　not　be　found　out　and　its　evaluation　on　stability　was　unsafe　by　using　the　commercial　software.　Furthermore,　during　calculating　the　interior　stability　of　soil-nailed　structure,　the　soil　deposit　was　commonly　regarded　as　homogeneous.　In　this　paper,　the　stratified　character　of　soil　deposit　was　considered.