Metallophthalocyanine　(MPc)　and　its　composites　have　excellent　photo-electricity　properties.　Here　we　report　the　study　of　MPc　doped　silica　xerogel　matrix　obtained　by　sol-gel　technique.　Because　the　issue　of　dimerization　is　vital　in　determining　the　optical　properties　of　dye　doped　sol-gel　materials　and　MPc　offers　an　excellent　opportunity　to　characterize　dimers　from　monomers　because　of　their　identified　absorption　bands,　we　studied　the　dimerization　of　different　kinds　of　MPc　doped　silica　composites　using　electronic　absorption　spectra.　Changes　in　the　absorption　spectra　were　correlated　with　various　stages　of　the　sol-gel　process.　The　results　show　that　in　the　composite　MPc　molecules　concurrence　in　forms　of　monomer　and　dimer,　and　dimerization　is　bad　during　the　latter　stages　of　drying　because　of　the　rapid　decrease　of　remaining　solvent　and　its　ethanol/water　ratio.　To　overcome　this　problem,　a　kind　of　dissociating　agent　Cremophor　EL　is　added　in　order　to　protect　the　Zinc　tetrasulfo-phthalocyanine　molecules　from　dimerization.　In　the　other　hand,　a　newly　developed　in　situ　synthesis　technique　was　successfully　introduced　to　synthesize　MPc　during　the　sol-gel　process.　It　is　found　that　the　in　situ　synthesized　MPc　only　exist　in　the　form　of　monomer　in　the　composites.　(C)　2003　Elsevier　Science　B.V.　All　rights　reserved.