A　photosensitizer　tetra-alpha-(2,4-di-tert-butylphenoxy)-phthalocyaninato　zinc　[ZnPc(OAr)(4)]　was　successfully　encapsulated　in　SiO2　nanoparticle　by　the　microemulsion　method.　The　photosensitized　composite　nanoparticle　was　able　to　degrade　2,4,6-trichlorophenol　(TCP)　in　aqueous　solution.　Under　visible　light　irradiation,　the　nanoparticles　efficiently　generated　reactive　oxygen　species;　95.4%　of　TCP　was　degraded　after　270　min　of　reaction.　Some　aromatic　compounds　and　aliphatic　carboxylic　acids　were　detected　by　mass　spectrometry　as　the　reaction　intermediates.　The　results　were　different　from　those　of　previously　reported　photocatalytic　reactions,　in　which　valence　band　holes　or　hydroxyl　radicals　functioned　as　the　main　oxidants.　The　photosensitizing　composite　nanoparticle　is　potentially　applicable　to　the　oxidation　of　phenol.