We　report　here　the　study　of　aluminum　tetrasulfo-phthatocyanine　chloride　(AlTSPcCl)-doped　silica　xgel　obtained　by　sol-gel　technique.　Because　the　issue　of　dimerization　is　vital　in　determining　the　optical　properties　of　dye　doped　sol-gel　materials　and　phthalocyanine　offers　an　excellent　opportunity　to　characterize　dimers　from　monomers　because　of　their　identified　absorption　bands,　we　study　the　dimerization　of　different　concentrations　of　AlTSPcCl-doped　composites　by　electronic　absorption　spectra.　Proceeding　of　the　absorption　spectra　was　correlated　with　various　stages　of　the　sol-gel　process.　The　results　show　the　composites　AlTSPcCl　concurrence　in　the　forms　of　monomer　and　dimer.　Dimerization　behaves　differently　in　the　early　and　latter　stage　of　sol-gel　transition.　Two　reasons　are　given　from　the　change　of　the　micro-environment　in　which　AlTSPcCl　existed　during　the　sol-gel　process.　(C)　2002　Elsevier　Science　B.V.　All　rights　reserved.