To　overcome　the　defects　of　the　single　parameter　m　method　which　the　current　specification　recommended,　put　the　composite　stiffness　principle　and　bi-parameter　method　that　applied　to　piles　subjected　to　laterally　concentrated　loads　extended　to　calculate　the　deformation　and　internal　force　on　internal　braces　retaining　structure　in　deep　excavation.　Based　on　the　principle　and　the　method,　the　modified　finite　difference　solution　of　beam　on　elastic　foundation　was　presented.　In　addition,　the　incremental　method　was　introduced　to　consider　the　dynamic　construction　process.　The　composite　stiffness　EI　and　bi-parameters　m　and　n　were　obtained　through　the　back　analyses　from　the　field　measurement.　The　result　showed　that　both　the　calculated　horizontal　displacement　and　bending　moment　by　the　method　proposed　in　this　paper　were　in　good　agreement　with　the　measured　data.　In　contrast,　the　result　by　the　current　single-parameter　method　was　unsatisfactory.　The　parameters　obtained　through　the　back　analyses　can　be　applied　to　the　uniform　structures　in　the　same　foundation　pit　or　similar　retaining　structures　and　engineering　geological　conditions　in　the　same　areas.　Undoubtedly　it　can　obtain　more　accurate　results　than　the　current　single　parameter　method.　©　2016,　Science　Press.　All　right　reserved.