Abstract: The present disclosure provides a packed rotating biological contactor and a method for ammonia nitrogen conversion based on the packed rotating biological contactor. The packing frame of the packed rotating biological contactor provided in the present disclosure is formed by engaging two meshed disks, the hollow structure thus formed can be filled with packings, increasing the tilling amount of the packings; the selection of packing types can improve the film-forming rate of microorganism and shows a good adsoiption effect on the microorganism, so that the biofilm formed on the surface of packings can resist the impact of water flow and avoid shedding. The selection of disk meshes and packing types also increases the specific surthce area of the packed rotating biological contactor, which can improve the acclimation efficiency of microorganisms and enable the packed rotating biological contactor to carry more microorganisms, thus forming biofilms with excellent performance.