Landfill leachate was treated by A/O-coagulation-BDD combined processes, and the organic matters during treatment processes were characterized by UV spectra, fluorescence excitation-emission matrix, GC-MS, and Fourier transform infrared spectra under optimum operating conditions. Aliphatic organic matters, tryptophan-like matters, and some fulvic acid-like organic matters can be easily removed by A/O treatment while humic acid-like organic matters can not. The removal efficiencies of ryptophan-like matters and fulvic acid-like organic matters were better as HRT increasing from 4.0 d to 10.7 d. As sludge recirculation ratio increasing from 3.0 to 3.5, the removal efficiency of ryptophan-like matters was better while the removal efficiency of fulvic acid-like organic matters was worse. Coagulation mainly removed aliphatic organic matters, proteins, and some humic acid-like organic matters, but can’t easily remove fulvic acid-like organic matters, and there were still some aroma organic matter in the effluent. BDD treatment can effectively remove kinds of refractory organic matters.