Delamination　is　one　of　the　failure　modes　of　functionally　graded　materials　(FGM),　resulting　in　the　critical　change　of　vibration　characteristics.　The　Chebyshev　polynomials　are　commonly　used　as　admissible　functions　to　improve　the　computational　efficiency　of　numerical　algorithms　and　avoid　the　occurrence　of　ill-conditioned　problems.　This　paper　extends　the　Chebyshev-Ritz　method　to　the　free　vibration　analysis　of　delaminated　FGM　plates,　in　which　the　material　variation　through　the　plate　thickness　follows　the　exponential-law　distribution.　A　plane　crack　that　is　considered　to　be　perpendicular　to　the　thickness　direction　penetrates　through　the　width　direction.　Based　on　the　region　approach,　the　analysis　of　FGM　plates　with　a　mid-plane　delamination　is　divided　into　four　sub-regions.　The　kinetic　energy　and　potential　energy　of　each　sub-region　are　derived　by　the　thin　plate　theory　and　von　Karman　nonlinear　strain-displacement　relation.　The　modal　functions　of　the　displacement　fields　of　FGM　plates　can　be　constructed　in　accordance　with　the　displacement　continuity　conditions　of　the　delamination　interface　and　the　boundary　conditions　of　such　plates.　The　effects　of　asymmetric　material　distribution,　delamination　length　ratio,　Young＇s　modulus　ratio,　and　boundary　support　on　the　vibration　behavior　of　FGM　plates　are　investigated.　This　semi-analytical　study　provides　a　reasonable　theoretical　basis　for　the　behavior　prediction　and　delamination　identification　of　composite　structures.