In recent years, the newly planned sewage treatment plants mostly adopt biologicaltreatment system which can remove nitrogen and phosphorus at the same timeCombined with membrane bioreactor (MBR). The purpose is to make the treated drainage water available as reclaimed water. The membrane bioreactor (MBR) is acombination of traditional active fouling process and membrane technology, it's a biological process. However, due to the high concentration of MBR (mixed liquorSuspended solids, MLSS), so the film fouling phenomenon in practical application is its operation and design the problem. At present, the relationship between microbial phase change and membrane fouling in MBR is very important department, always unable to get an answer.