Three-dimensional excitation-emission matrix fluorescence technology and parallel factor analysis were conducted to investigate the spectral characteristics and pollution source of dissolved organic matter (DOM) in a subsurface flow-surface flow combined constructed wetland in north China. This study provided a scientific basis for further revealing the chemical behavior and ecological effects of DOM in constructed wetlands. A similar fluorescence pattern was observed from different stages in the constructed wetland. Both humic-like peak and protein-like peak appeared with different intensities. The fluorescence intensity of humic-like and protein-like compounds decreased by coagulation sedimentation. The fluorescence spectrum of effluent from subsurface flow wetland suggested that the intensity of protein-like peaks, microbial metabolic by-product peaks, and tryptophan-like peaks significantly decreased. It stated that subsurface flow wetlands could achieve the effective degradation of proteinoid substances in the river. However, the subsurface flow wetlands possessed poor degradation ability on humic-like substances. The weaker intensity of the protein-like peak and the humic acid-like peak in the surface flow wetland was observed, and the weakest intensity spot was found at 3 km downstream of the subsurface wetland. This trend was attributed to the microbial degradation on the surface of the membrane and the adsorption of aquatic plant roots. Five fluorescent components were identified by PARAFAC, including fulvic-like component C1(240, 330/430 nm), humic-like component related to microbial activity C2(285, 330/380 nm), tryp to phan-like component C3(230/350 nm), microbial metabolic by-product component C4(280/320 nm) and terrestrial humic-like component C5(270, 380/470 nm). Multi indexes of the fluorescence spectrum were calculated for the DOM source analysis in the wetland. Both the fluorescence index and the autochthonous index of water samples indicated that the main source of DOM in the wetland was from biological metabolism and the terrestrial input had negligible influence. The humification index showed that the wetland had weak humification. Spearman correlation analysis suggested that the five fluorescent components were homologous and closely related to the migration and transformation of nitrogen in the water.