In this study, the authors carried out sorption experiment with the purpose of understanding the effects of different relative molecular masses of dissolved organic matter (DOM) on PPCPs adsorption behavior. The authors chose carbamazepine (CBZ) as the target pollutants and quartz sand as the inorganic minerals, and used commercial humic acid (HA) to prepare DOM with ultrafiltration classification. Then the authors studied the impact of HA with different relative molecular masses on CBZ adsorption behavior based on fluorescence spectrum and infrared spectroscopy. It is found that, through ultrafiltration classification technology by 3 000 and 10 000 ultrafiltration membranes, the structures of HA are different. Large molecular weight fractions of HA which contain more hydroxyl and benzene ring are mainly hydrophobic substance with better stability and high degree of aromatic tectonics. However, the structure of HA with medium and small molecular weight is not very different. They contain more oxygen-bearing functional groups such as carbonyl and carboxyl groups which are mainly hydrophilic substances. DOM has a significant effect on the adsorption of CBZ onto quartz sand. Large molecular weight DOM promotes the adsorption of CBZ on quartz sand, while medium and small molecular weight DOM inhibits the adsorption of CBZ on quartz sand. The reason is that the large molecular weight DOM can bind on the mineral surface which increases the activity of adsorption sites on the dielectric surface and its aliphatic and aromatic substances have hydrophobic interaction with hydrophobic groups of CBZ. These effects make CBZ adsorb or accumulate on the surface of the medium, which promotes the adsorption of CBZ in quartz sand. The polar functional groups of small and medium molecular weight DOM can bind to the amide of CBZ through polar interaction and increase the solubility of the CBZ molecules, thus inhibiting the adsorption of CBZ on the quartz sand.