A method for treatment of sludge with a facultative-organism-adapted membrane bioreactor by providing a sludge treatment system comprising a facultative digestion tank, a membrane module, an aeration system, a sludge pump, and a drainage pump, pumping sludge into the facultative digestion tank via the sludge pump and allowing for digestion, synchronously aerating and scouring the membrane module by the aeration system, pumping the sludge by the drainage pump and filtrating by the membrane module so that sludge and water are separated, and draining the water via the drainage pump. The method can digest sludge completely in the digestion tank, and solves problems existing in conventional sludge treatment methods such as large investment and high transportation cost, even achieves a subject of zero discharge of sludge.