Membrane bio-reactor (MBR) is an innovative and effective wastewater treatment process, which has much more extra advantages than other processes. However, membrane fouling and high operational/maintenance costs are always two important factors that restrict the development of MBR. In order to alleviate membrane fouling, larger aeration rate is usually used, which increases the operational cost and decrease N and P removal efficiencies of MBR. This paper summarizes the pilot scale experimental study on the improvement of operational performance of MBR by its design modification from one cell into three cells with micro-aeration,normal aeration and enhanced aeration conditions respectively with the package of fibrous bio-film carrier and PAC. As the result, the effluent water quality was improved significantly and membrane fouling was alleviated remarkably.