As a widely investigated issue in sewage treatment, the efficient and stable removal of carbon, nitrogen, phosphorus, and other pollutants is the ultimate goal of biological wastewater treatment process control and optimization. A microbial community with reasonable composition and distribution and a dynamic response to changes in important control parameters is the key to achieving this goal. After sampling 19 typical sewage treatment processes in six large cities in China during summer and winter, the results of MiSeq high-throughput sequencing and the Microbial Database for Activated Sludge（MiDAS）comparison and classification showed that the core communities in Chinese sewage treatment processes were significantly similar： 29 genera could be observed in all 38 samples, while 1 901 genera were found in 1 or a few （