Abstract: Taking the raw water of the Yangtze River as the simulated object, polyaluminum chloride (PAC) as the coagulant, and PAC/polydimethyldiallylammonium chloride (PDMDAAC) as the composite coagulant, the simulated raw water containing nitrogen disinfection by-product N-nitrosodimethylamine (NDMA) was used for coagulation treatment (coagulant treatment) and enhanced coagulation treatment (composite coagulant treatment), and the correlation between the water quality parameters (turbidity, CODMn, organic amine and ammonia nitrogen) and the NDMA removal rate in the simulated raw water after treatment was compared. Combined with the analysis of the microstructure, functional group properties and coagulation mechanism of the SEM characterization of pollutants representing water quality parameters, the removal mechanism of NDMA was speculated. The results showed that the water quality parameters and NDMA removal rate of various simulated raw water increased first and then stabilized or slightly decreased with the dosage increase of coagulant or composite coagulant after coagulation and enhanced coagulation treatment. The maximum removal rate of NDMA (5.88%~15.65% and 6.48%~16.90%) of one-component simulated raw water (containing NDMA and one of the four simulated pollutants (diatomite, sodium humate salt, dimethylamine hydrochloride and ammonium nitrate) was higher than that of NDMA containing only by (4.31% and 4.88%). The maximum removal rate of NDMA in multi-component simulated raw water (containing NDMA and four simulated pollutants (diatomite, sodium humate salt, dimethylamine hydrochloride and ammonium nitrate) was the highest (39.15% and 42.04%). The four pollutants adsorbed NDMA to different degrees based on their different microstructures and surface functional group characteristics. The electric neutralization and adsorption bridging effects generated by coagulants and composite coagulants can remove free and adsorbed NDMA by pollutants. The adsorption and synergistic adsorption of pollutants and the enhanced coagulation of composite coagulants significantly enhanced the removal of NDMA.