In　the　traditional　interaction　factor　method,　only　the　elastic　settlement　of　pile　groups　can　be　calculated,　and　the　interaction　factors　are　significantly　greater　than　the　real　results.　Using　3D　numerical　simulation　method　to　fit　the　the　load-settlement　curve　of　a　single　pile,　the　elastic　parameters　of　soil　and　pile-soil　interface　parameters　are　determined　through　the　elastic　and　elasto-plastic　analyses.　Then　by　establishing　a　two-pile　model,　the　influences　of　various　parameters　such　as　the　load　level　on　pile　top,　ratio　of　pile　spacing　to　pile　diameter,　modulus　ratio　of　pile　to　soil,　modulus　ratio　of　pile　tip　soil　to　surrounding　soil,　pile　slenderness　ratio　and　existence　of　the　third　pile　between　two　piles　on　the　interaction　factors　are　analyzed,　and　a　polynomial　curve　is　used　to　fit　the　results.　Based　on　the　results　of　numerical　analysis　and　field　tests,　a　method　using　single　pile　load　tests　to　calculate　the　elastic　and　elasto-plastic　settlement　of　pile　groups　in　the　interaction　factor　method　is　proposed,　and　it　is　extended　to　compute　the　nonlinear　settlement　of　pile　groups.　Analysis　of　an　engineering　case　shows　that　the　load-settlement　curve　computed　by　the　proposed　method　agrees　well　with　the　measured　one,　and　the　proposed　method　can　save　a　lot　of　computing　time　than　the　conventional　numerical　simulation　and　is　suitable　for　the　analysis　and　design　of　large-scale　piled　raft　foundation　with　large　pile　spacings.　©　2016,　Chinese　Society　of　Civil　Engineering.　All　right　reserved.