Effects of potassium permanganate (PP) oxidation on natural organic matter(NOM) chlorination activity was studied in the article. Natural organic matter was separated into humic acid (HA), fulvic acid(FA), hydrophilic acid(HPIA) and non-hydrophilic acid (HPI-NA) fraction four fractions by XAD resin adsorption technique. Potassium permanganate oxidation alone increased HA and HPIA chlorination activity and decrease that of FA and HPI-NA. The chlorination activity of HA and HPIA were increased by 39.3% and 13.8% by 0.75 mg/L. potassium permanganate, but the chlorination activity of FA and HPI-NA were decreased by 33.6% and 46.9%. SUVA results showed that potassium permanganate increase FA and HPIA unsaturated band contents, and decreased that of FA and HPI-NA. Compared with coagulation, potassium permanganate combined with coagulation can decrease the trihalomethanes of HA, FA, HPIA and HPI-NA by 9.1,15.7,7.2 and 14.7 per cent compared with that of coagulation alone.