Natural organic matter must be characterized to understand its role in drinking water treatment. The variation of Natural organic matter in different unit processes of full scale drinking water treatment plants in Korea was investigated for three years and compared between conventional and advanced drinking water treatment. Natural organic matter characteristics are determined by liquid chromatography-organic carbon detection, biodegradable dissolved organic carbon, and specific UV absorbance. Raw water sample's dissolved organic carbon of August was approximately 200 µg/L higher than that of January. The removal of dissolved organic carbon in January and August was similar in the range from 40 to >99%. Biopolymer fractions showed seasonal variations during drinking water treatment. Moreover, the removal of building block and low molecular weight neutrals was different between advanced and conventional drinking treatment processes.