Chromophoric　dissolved　organic　matter　(CDOM)　plays　important　roles　in　aquatic　environments,　and　its　optical　properties　provide　a　series　of　indices　for　evaluating　the　source　and　composition　of　dissolved　organic　matter　(DOM).　However,　little　is　known　about　the　varying　photodegradation　of　CDOM　from　different　sources　and　the　effects　on　the　optical　indices　of　DOM　composition.　This　was　studied　for　typical　natural　and　anthropogenic　sources　(plant　and　leaf　litter　leachates,　the　influent　and　effluent　of　a　wastewater　treatment　plant,　and　a　river).　The　CDOM　absorption　(a(280))　showed　a　lower　degradability　for　the　plant　leachate　than　other　sources,　mainly　due　to　its　low　molecular　weight　and　aromaticity.　Four　fluorescent　components　were　identified　with　excitation-emission　matrices-parallel　factor　analysis　(EEMs-PARAFAC),　namely　benzoic　acid/monolignol-like　C1,　humic-like　C2　and　C3,　and　tryptophan-like　C4.　The　plant　leachate　contained　mainly　C1,　which　was　photodegraded　moderately,　while　other　sources　had　more　C2　and　C3　with　higher　photodegradability.　C4　was　photodegraded　in　most　sources　but　was　photoproduced　in　the　leaf　litter　leachate.　The　absorption　slope　(S275-295)　and　slope　ratio　(S-R)　increased　while　the　humification　index　(HIX)　decreased,　suggesting　a　decreasing　molecular　weight　and　humic　content　by　photodegradation.　This　was　consistent　with　the　decreasing　%C2　and　%C3　but　increasing　%C4,　which　indicated　preferential　removal　of　humic-like　components.　The　%C1,　%C2,　biological　index　(BIX),　and　fluorescence　index　(FI)　were　less　affected　by　photodegradation　than　other　indices　for　most　sources.　These　results　have　implications　for　a　better　understanding　of　the　photochemistry　of　CDOM　and　the　applications　of　optical　indices.