The working principle of MBBR filter media: when the wastewater passes through the fluidized bed packing reactor, the microorganisms in the water constantly adhere and grow on the inner and outer surface of the fluidized bed packing, forming a biofilm. The biofilm can fully contact with the pollutants in the water and decompose them, so that the water quality can be purified. The turnover of the mixture and the movement of the carrier are realized by aerobic aeration or anaerobic stirring.