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Compared with the traditional activated sludge process, the Membrane Biological Reactor （MBR） has the advantages: less space occupancy, easily control, higher sludge concentration, higher oxygen transfer efficiency, better effluent and less excess sludge. The dissertation has researched the effect of the Membrane Biological Reactor on the domestic sewage and the impact of the organic load, DO, pH on the system. At the same time, the membrane pollution, the cleaning efficiency and the membrane resistance have been studied. The removal efficiency of COD, NH3-N, TN has increased along with the increasing of sludge concentration. With the enhancing of membrane’s withholding, the COD concentration of effluent has no more change. The COD increasing of influent makes the removal effect of COD, NH3-N, TN increase, but the membrane flux decreased rapidly. The COD concentration of effluent does not change when the COD concentration of influent renews, but the removal efficiency of NH3-N and TN decreases and the membrane flux can not renew. The variety of DO, pH in definite range has less impact on the removal effect of COD whereas more on the removal efect of NH3-N, TN. In the experiment of organic wastewater, the membrane withholds the slowly degraded accumulate in the that of the influent organic nitrogen, which makes the nitrogen reactor. Subsequently, the TN of effluent is higher than and the removal effect of nitrogen turns bad. The membrane total resistance includes the membrane resistance Rm, the concentration polarization resistance Rb1, and the resistance because of membrane pollution Rf,. The Rm is generally correspond with Rf. The Rb1 is the highest of them, above half of total resistance （50.76%）. In the MBR system, the membrane flux decreases rapidly increasing of membrane filtrate resistance because of the along with filter cake coherent sludge on the surface of membrane. The aerator has some benefit to the renewing and increasing of membrane flux. The lower suspended sludge concentration was retained by adding filler in the Membrane Bioreactor, thus high membrane flux and excellent effluent quality were kept. The ratio of Rc（cake resistance） to R（total resistance） was declined to 10% and the ratio of the resistance affected by dissolved organic
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