Abstract: The membrane-fouling problem when operating an integrated membrane bioreactor was investigated,the effects of different physical washing methods was studied,and membrane fouling reasons as well as countermeasures was discussed.The result showed that adhesion of sludge layer on membrane external surface was main factor for membrane fouling.Rubbing the membrane thread with hands was a convenient physical washing method and could be applied to membrane bioreactors at full scale,and this process could remove membrane’s exterior sediment and recover normalization membrane specific flux from 0.29 to 0.64,however continued aeration without filtration could only recover normalization membrane specific flux from 0.26 to 0.39.The increasing rate of least residual suction pressure during time-off of intermittently operated membrane could be used to evaluate the membrane filtration characteristic of membrane process.