A method for forming a facultative-organism-adapted membrane bioreactor by: providing a membrane bioreactor having a membrane module, aerating intensively the membrane module at a lower part thereof and maintaining the scouring against the membrane module so that an aerobic environment is formed at a middle and lower part of the membrane module, and controlling aeration intensity so that a facultative or anaerobic environment is formed around the membrane module excluding the middle and lower part thereof. The a facultative-organism-adapted membrane bioreactorformed by the method has low energy consumption, low sludge yield coefficient, and high efficiency of nitrogen and phosphorus removal.