Abstract: An anoxic-oxic membrane bioreactor (MBR) combination technology was used for treating campus domestic sewage. The sludge samples were collected every 24 hours to analyze the structure of biotic community and species composition in different periods. Meanwhile, the indicators of the sewage effluent and sludge quality were monitored and the relationship between biotic community structure and the removal rates of COD_Cr, NH₄⁺-N and TP were studied. The results showed that during the running time, the flocculate structure of activated sludge changed among close-loose-tight-bulking, and the number of filamentous bacteria gradually increased, changing from 0 level, ±level, + level to ++ level.The change of the fauna community-Vorticellidae,Rotifera,Epistylis insects was found to have relation with sludge structure, and so the fauna community could be used as the indicator of sludge bulking as well as the time point of sludge discharging. The population size of microfauna and dominant fauna varied with the water quality, and the population of Sessile Vorticellidae,Cyst and Epistylis could be used as the bioindicator of COD_Cr concentration of the effluent.The dynamic relationship between the removal rates of NH₄⁺-N,TP and microfauna community structure was not significant.