Hydrophobic　organic　contaminants　(HOCs)-pyrene,　and　natural　organic　matters　(NOM)　from　different　sources　were　taken　as　the　test　compounds　to　investigate　the　impact　of　physicochemical　characteristics　of　NOM　on　HOCs＇　partition　to　the　NOM　in　this　study.　The　effects　of　solution　property,　NOM　characteristics,　and　modi.　cation　by　ozone　preoxidation　on　pyrene　partition　to　NOM　were　systematically　evaluated.　According　to　the　fluorescence　quenching　method,　the　partition　coefficient　K-oc　of　pyrene　to　NOM　was　calculated,　which　was　found　to　have　a　great　relationship　with　the　aromatic　structures　and　hydrophobic　functional　groups　of　the　NOM.　The　NOM　characteristic　modi.　cation　corresponding　to　solution　property　could　influence　the　interactions　between　the　NOM　and　pyrene.　Preozonation　could　destroy　the　aromatic　or　hydrophobic　structures　of　the　NOM　and　decrease　K-oc　of　pyrene.