This　research　aims　to　analyze　the　imperfection　sensitivity　in　the　nonlinear　resonance　behavior　of　bi-directional　functionally　graded　(BDFG)　porous　beam.　The　trigonometric　and　hyperbolic　functions　are　chosen　to　describe　the　global　and　localized　geometrical　imperfections.　Considering　the　first-order　shear　deformation　theory　and　von-Karman＇s　geometric　nonlinearity,　theoretical　model　is　formulated　to　depict　the　coupled　motion　including　the　stretching,　bending　and　shear　deformations　of　BDFG　porous　beam.　Differential　quadrature　based　Galerkin＇s　procedure　is　proposed　to　formulate　the　reduced　model.　The　nonlinear　responses　are　obtained　by　using　the　numerical　bifurcation　method.　Numerical　results　demonstrate　that　resonance　response　of　beam　under　goes　cyclic-fold　bifurcations.　Resonance　behavior　of　beam　may　exhibit　hardening,　softening　or　softeninghardening　type　nonlinearity.　Imperfection　sensitivity　analysis　shows　that　the　variation　of　imperfection　modes,　material　gradient　and　porosity　change　the　characteristic　of　frequency-response　and　force-response　or　even　the　number　of　bifurcation　points.　.