A　new　kind　of　step　tapered　hollow　pile　with　huge　diameter　was　successfully　applied　in　the　stratum　with　bead-like　karst　caves.　The　load　transfer　mechanism　of　the　pile　is　complicate.　According　to　the　analysis　of　the　load　transfer　characteristics　of　the　pile,　the　effect　of　enhancement　of　the　resistance　at　variable　cross-section　to　the　shaft　resistance　was　revealed.　A　new　load-transfer　function　model　for　step　tapered　hollow　pile　with　huge　diameter　was　proposed　on　the　basis　of　disturbed　state　theory.　The　bearing　capacity　at　variable　cross-section　was　analyzed,　and　the　enhancement　effect　of　shaft　resistance　caused　by　the　end　resistance　was　presented.　An　approach　for　calculating　the　enhancement　coefficient　α　was　proposed　on　the　basis　of　Mindlin＇s　solution　in　semi-infinite　space.　The　proposed　analytical　solution　was　verified　by　comparing　with　the　numerical　results　and　two　existing　analytical　solutions.　In　the　new　load　transfer　model,　the　hyperbolic　model　and　parabola　model　were　selected　to　describe　the　relative　intact　state　of　pile-soil　interface　located　on　the　pile　side　and　the　pile　tip　respectively,　and　Mohr-Coulomb　model　was　used　to　assume　the　fully　adjusted　state.　Thus,　the　load-transfer　function　model　of　pile-soil　interface　was　proposed　systematically.　The　effect　of　the　model　parameters　was　analyzed　numerically.　The　proposed　calculation　model　was　found　to　be　an　excellent　to　describe　the　behavior　of　the　step　tapped　hollow　pile　with　large　diameter.　The　resistance　at　variable　cross-section　has　a　significant　enhancement　effect　on　the　shaft　resistance.　The　load　transfer　function　model　based　on　the　Disturbed　State　Concept　theory　can　describe　the　nonlinear,　hardening　and　softening　characteristics　of　pile-soil　interface.　The　enhancement　effect　of　the　shaft　resistance　caused　by　the　resistance　at　variable　cross-section　can　be　revealed　obviously.　©　2018,　Science　Press.　All　right　reserved.