Three dimensional excitation-emission fluorescence spectra characteristics of influent and effluent from urban domestic sewage treatment plant were analyzed combined with PARAFAC model. The results indicated that urban sewage has four fluorescence centers. The 1 and 2 fluorescent center of influent were obvious. However, 3 and 4 fluorescence centers were blurry. All the four fluorescence centers of effluent were quite obvious. Combining PARAFAC model, both the influent and effluent contain three kinds of fluorescence compositions, which are tryptophan-like、 tyrosine-like and fulvic-like. The scoring values of three kinds of fluorescent compositions can be used as another fluorescence feature of urban sewage. According to the scoring values, tryptophan-like and tyrosine-like are unstable in both influent and effluent, but fulvic-like is relatively stable.