In　analyses　of　soil　structure　interaction　(SSI),　two-degrees-of-freedom　lumped-parameters　model　is　often　used　to　simplify　the　soil.　The　model　is　only　suitable　to　isotropic　elastic　soil,　but　the　soil　stratum　in　real　engineering　site　is　always　layered　and　anisotropic　one.　In　order　to　simplify　the　layered　soil　by　this　model,　this　article　provides　a　variably　damped　least　square　method　to　identify　the　parameters　by　using　the　actual　acceleration　records.　This　method　has　obvious　virtues　such　as　wide　range　of　application　and　high　computation　precision　and　can　be　used　to　handle　practical　soil-structure　interaction　problem.　And　the　corresponding　FORTRAN　programming　and　exemplary　analysis　is　carried　out　in　this　paper.