To improve treatment performance and alleviate membrane fouling, the physical and biological properties of sludge in combined MBR which divided into anoxic, anaerobic and aerobic zone were studied. During initial startup period, the sludge in A/A/O combined MBR was suspended growth, after textile carrier package, the sludge was suspended and fixed growth. The biomass analysis showed that with the increase of operation time, MLVSS/MLSS decreased from 0.93 to 0.72 which certified that high MLSS concentration caused biomass growth slow gradually, while packing textile carrier could supply attached biomass which maximum value was 0.18g/cm(3777.8mg/L). Meanwhile, high MLSS concentration also resluted in high sludge viscosity which could reach to 35.42mPa•s and decreased sludge activity. Particle size anaylisis showed that shear stress of aeration made the sludge flocs smaller than conventional activated sludge process. All the sludge properties which had been analysis in this study showed A/A/O combined MBR had great difference from conventional MBR process, and some parameters could be used for membrane fouling control in A/A/O combined MBR for wastewater treatment project.