Soil　is　a　complex　material　whose　properties　are　elastic,　plastic　and　viscious.　The　selection　of　a　proper　constitutive　relation　is　important　in　the　study　of　stratum　movement　induced　by　underground　excavation　in　modern　cities.　First,　based　on　the　Fast　Lagrangian　Analysis　of　Continua　(FLAC)　method,　the　elastic　response　stress　(p,　q)　distribution　induced　by　a　circular　tunnel　is　analyzed,　and　the　surrounding　soil　is　divided　into　four　categories:　p　increase　q　increase,　p　increase　q　decrease,　p　decrease　q　increase,　p　decrease　q　decrease　according　to　p-q　stress　path.　The　character　of　p-q　distribution　and　the　plastic　zone　induced　by　tunneling　in　clay　are　compared　when　the　Mohr-Coulomb　model　(M-C),　the　Drucker-Prager　model　(D-P)　and　the　Modified　Cam-Clay　model　(C-C)　are　adopted;　the　C-C　model　is　considered　to　be　suitable　for　simulating　underground　excavation　problems,　Second,　factors　such　as　stratum　character,　stress　path　and　relative　position　between　soil　and　excavation　are　thought　to　be　important　in　the　selection　of　a　proper　constitutive　relation,　accounting　for　the　geological　condition　of　Beijing　and　measuring　techniques　being　used　in　geotechnical　engineering.　Fine　grained　soils　such　as　clay　and　silt　can　be　modeled　by　the　C-C　model.　Coarse　grained　soil,　for　containing　and　not　containing　excavation,　may　be　represented　using　the　M-C　model　considering　strain　softening　and　the　normal　M-C　model.　Finally,　with　the　aid　of　FLAC　method　and　its　internal　language　FISH,　a　scheme　of　estimating　and　controlling　parameter　input　is　suggested.