To optimize anoxic aerobic (A/O) wastewater treatment process and improve effluent quality, the variations of soluble microbial products（SMP）in the treatment process is investigated. The fluorescence characteristics of SMP in A/O process are studied through ultraviolet-visible (UV-sis) spectra,fluorescence excitation-emission matrix (EEM), and the multivariate statistical method. The liner relationships between FRI and COD and NH⁺₄-N are analyzed. The composition and metabolism of the SMPs are studied. The results show that Pearson correlation indices between COD, ammonia nitrogen and normalized integral volumes of region Ⅰ and Ⅱ are both higher than 0.97. The humus-alike and the protein-like substances are the main fluorescence substances of the process. And the concentration of humus-alike remains at 40 × 10⁶ au·nm² in the aerobic stage, which is not totally removed in the A/O process. The concentration of the protein-like substances are reduced from 25.43% down to 2% by metabolism, and most of the protein-like substances are removed at the anoxic zone. The method could be used for rapidly monitoring the concentration of COD and the composition of organic matter in water, which provides technique reference for the improvement of A/O process parameters.