To analyze the effect of sludge fermentation liquid, using as internal carbon source, on microbial community structure in anaerobic-anoxic-aerobic process, three-month-long operational experiment was conducted at flow ratio of fermentation liquid and domestic wastewater 1∶35 at room temperature. The clustering analysis indicated that the microbial community structure was changed significantly by fermentation liquid, and the microbes of 5-30 d and 45-90 d had quite different homology. The microbial diversity analysis demonstrated that the Shannon-Wiener index increased from 2.6 to 3.1, resulting in the enhancement of operational stability. Meanwhile, fermentation liquid appeared to be selective for ammonia-oxidizing bacteria Nitrosomonas sp., nitrifying bacteria Betaproteobacteria and Nitrospira sp., denitrifying bacteria Comamonas sp. and phosphorus-accumulating bacteria Gammaproteobacteria, which led to the TN and TP removal efficiency improved from 64.5％ and 52.4％ to 84.7％ and 94.3％, respectively.