The influence of hydraulic retention time (HRT) on characteristics of dissolved organic matter (DOM) in membrane bioreactor used for restaurant wastewater treatment was studied through gel filtration chromatography (GFC) and excitation-emission matrix fluorescence spectra analysis,. Results showed that the second peaks in GFC spectra of the effluent samples gradually moved to the direction of the smaller molecular weight distribution. The molecular weight distribution became broader with the decrease of HRT. Meanwhile, molecular weight distribution of extracellular polymeric substances (EPS) in sludges was less affected by HRT. The main fluorescent materials in raw water were high- and low-excitation wavelength tryptophan. However, the primary fluorescent substances in effluents were UV- and visible fulvic-like. With the decrease of HRT, high-excitation wavelength tryptophan occurred in effluents of No. 4, 5 experimental devices. It was also found that the center of this tryptophan peaks were red-shifted by 5 nm and 10 nm along the emission axis compared with the influent wastewater, respectively.