To reveal the relationship between microorganism and pollutants’ degradation in the stability system of the municipal wastewater treatment plant,the dynamic monitoring of microbial community structure and metabolic activity of the stable operation biological system in biological wastewater treatment plant was carried out using the denaturing gradient gel electrophoresis(PCR-DGGE) and Biolog Technology.The results showed that the average removal efficiency of effluent COD,NH4+-N and TN was more than 84.4%,84.7% and 59.8%,respectively.The microbial community structure was stable in the different sites of biological system in the same season,and the ecological niche of predominant functional species including Bacillus,Pseudomonas,Aeromonas was stable.As the temperature increased in spring,the quantity and diversity of population increased significantly.Meanwhile,metabolic activity strengthened in bioloical system,which could improve the removal rates of pollutants.It is feasible to use the two methods to monitor the changes of microbial community structure of biological system in a wastewater treatment plant at low temperature.