Abstract: Membrane fouling is one of the main constraints of the application and development of membrane bioreactor. Therefore，as a case of using membrane bioreactor （MBR） to treat houshold sewage in a residential area，three operational parameters，such as addition of PAC，mixed liquid suspended solid（MLSS） and aeration rate（Q） were chosen to perform orthogonal experiments of three-factors-four-levels in order to study the optimum operation condition of MBR. The results showed that addition of PAC，mixed liquid suspended solid（MLSS） and aeration rate（Q） were 2g/L，7 g/L，6m3/h respectively. A parallel contrast experiment indicated that maximum membrane pressure difference reached 21.05kPa. Meanwhile，there was a linear relationship between protein/polysaccharide formation (the cause of membrane fouling) and increased membrane pressure difference.