The ceramic microfiltration system with periodic N-2-back-flushing was operated for treating paper wastewater discharged from a company making toilet papers by recycling milk or juice cartons. Two kinds of alumina membranes with 7 channels used here for recycling paper wastewater. The optimal N-2 filtration time for HC04 membrane with 0.4 mu m pore size was lower value of 4 min than 16 min for HC10 with 1.0 mu m pore size at fixed back-flushing time 40s, trans-membrane pressure 10 kg cm(2) and back-flushing pressure 5.0 kg cm(2). From the results of TMP effect at fixed filtration time and back-flushing time, the lower TMP was better on membrane fouling because high TMP could make easily membrane cake and fouling inside membrane structure. However, we could acquire the highest volume of total permeate for the reason that TMP was driving force in our filtration system to treat paper wastewater. Then the permeate water of low turbidity was acquired in our microfiltration system using multichannels ceramic membranes, and the treated water could be reused in paper process.