In　this　paper,　the　resonance　behavior　of　initial　imperfect　functionally　graded　material　(FGM)　cylindrical　shells　with　the　clamped-clamped　boundary　condition　at　two　ends　is　investigated.　The　material　properties　considered　here　are　graded　in　the　thickness　direction　according　to　a　simple　power　law　in　terms　of　the　volume　fractions　and　are　affected　by　temperature.　The　classical　deformation　theory,　von-Karman　type　nonlinear　geometric　relations　and　Hamilton＇s　principle　are　employed　to　derive　nonlinear　partial　differential　equation　of　the　clamped　circular　cylindrical　shell　at　two　ends.　The　partial　differential　governing　equations　are　truncated　by　the　Galerkin　technique.　Under　the　effect　of　transverse　external　excitation　and　in-plane　force,　averaged　equations　in　term　of　polar　coordinate　are　obtained　by　using　multiple　scales　method.　It　is　assumed　that　the　dynamic　system　is　in　the　case　of　primary　resonance　and　1:2　internal　resonance.　The　effects　of　the　volume　fraction,　temperature,　damping,　imperfection,　transverse　external　excitation　and　in-plane　force　on　amplitude　frequency　response　of　FGM　cylindrical　shell　with　initial　imperfection　are　studied　in　detail　by　the　application　of　numerical　continuation　method.　With　varying　the　tuning　parameter　of　the　excitation　frequency,　saddle　node　bifurcation,　hopf　bifurcation,　saddle　node　bifurcation　and　hopf　bifurcation　are　detected.