We　report　here　the　study　of　the　optical　limiting　mechanism　of　phthalocyanine(H2Pc)　and　different　kinds　of　metallo-　phthalocyanine(MPc)　in　silica　gel　glass　matrix.　Prepared　by　sol-gel　technique,　the　H2Pc　or　MPc　doped　silica　gel　glass　composites　were　transparent　and　homogeneous　with　the　required　regular　shape.　The　optical　limiting　behaviors　of　the　composites　were　measured　at　532　nm　with　8　ns　pulses.　The　results　show　that　among　three　samples　of　H2Pc,　NiPc　or　PbPc　doped　composites,　PbPc　has　the　most　obviously　optical　limiting　effect　owing　to　the　heavy　atom　effect.　Besides,　PbPc　has　better　optical　limiting　properties　in　solid-state　silica　gel　glass　matrix　than　in　liquid-state　DMF　solution.　Fluorescent　ZnTSPc　or　GaPcCl　doped　composites　have　little　optical　limiting　effect.　The　reasons　are　discussed　from　the　view　of　excited　physical　process　and　the　implied　mechanism　is　given.　©　2005　Elsevier　B.V.　All　rights　reserved.