By 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. It was found that the introduction of NOM fractions exept for NOM5K-10K and NOM3K-5K slightly decreased the removal efficiency of BPA which is 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,and NOM1K-3K),promoted its degradation due to the enhancement of chain reaction which is accompanied by the formation of hydroxyl radical,and the extent of promotion depended on the types and amounts of functional groups contained in NOM fractions.