Annular　flat　contact　interface　attached　with　torsion　pins　is　common　in　compressor　rotors　of　heavy-duty　gas　turbine.　To　study　the　torsional　behavior　of　annular　flat　contact　shaft　segment　attached　with　torsion　pins,　a　bilinear　model　of　torsional　deformation　is　proposed.　Numerical　calculation　with　three-dimensional　finite　element　model　is　conducted　to　validate　the　theoretical　model.　Then,　the　effects　of　pre-stress,　friction　coefficient,　number　of　pins　and　diameter　of　pin　on　the　key　parameters　of　the　bilinear　model,　such　as　the　torsional　stiffness　of　two　linear　segments,　the　torque　at　the　bilinear　inflection　point　of　two　linear　segments,　and　the　torque　loading　capability　of　contact　interface,　are　analyzed.　The　results　show　that　the　torsional　stiffness　before　the　slip　of　the　annular　contact　interface　is　almost　the　same　with　that　of　continuous　shaft　section,　however,　after　slip　it　is　determined　by　the　longitudinal　shear　stiffness　of　pins.　In　addition,　the　torque　at　the　bilinear　inflection　point　of　two　linear　segments　is　proportional　to　the　pre-stress　and　friction　coefficient.　©　2018,　Editorial　Office　of　Journal　of　Xi＇an　Jiaotong　University.　All　right　reserved.