Aquatic fulvic acid (FA) treated with ozone was characterized by physical/chemical (dissolved organic carbon-DOC), spectroscopic (UV/VIS, IR, fluorescence), chromatographic (gel permeation chromatography-GPC) methods. The influence of ozonation on the subsequent water treatment process such as flocculation and chlorination was also examined. The DOC concentration of the 20 min ozonated FA samples was reduced only a small amount (5%) whereas the UV absorption reduced to a higher percent (40%). The IR spectra of ozonated samples showed a moderate attenuation of the double band and aromatic character of FA. Ozonation of the FA caused the fluorescence intensities to increase steadily with ozonation tin-le, whereas it decreased when FA was flocculated after ozonation. Gel chromatographic characterization of FA showed that the high molecular weight (HMW) fractions were eliminated after flocculation followed by ozonation, while them apparent molecular weight (AMW) distribution of ozonated FA changed slightly. The formation potentials of trilialomethane (THMFP) and adsorbable organically bound halogen (AOXFP) were significantly decreased with the increasing ozonation time along with the flocculation process.