The aquatic NOM can be divided into different fractions in a wide range of molecular weight, which usually show different reactivity toward oxidants such as ozone. Fractioning natural organic matters (NOM) sourced from Songhua River with series of ultra membranes, the effect of each fraction on the degradation of BPA and NB by ozonation was investigated. The introduction of NOM fractions exept for NOM5K-10K and NOM3K-5K slightly decreased the removal efficiency of BPA which was highly reactive with ozone. On the contrary, for the refractory organic pollutant NB, NOM fractions especially the fractions with high molecular weight (NOM>10K、NOM5K-10K、NOM3K-5K、NOM1K-3K) promoted its degradation due to the enhancement of chain reaction which accompanied by the formation of hydroxyl radical, and the extent of promotion was dependent on the types and amounts of functional groups contained in NOM fractions. Even though this work is based on one type of NOM, the conclutions of this research are of general applicability.