The invention provides a preparation method of a suspended packing bioreactor. The preparation method comprises the following steps: (1) uniformly mixing 0.2-0.6 part by weight of magnetic powder, 7-10 parts by weight of recycled rubber powder, 3-12 parts by weight of zeolite, 2-8 parts by weight of maleic anhydride, 0.2-0.8 part by weight of dicumyl peroxide, 0.5-2 parts by weight of chitin, 3-5 parts by weight of powdered coke and 1-2 parts by weight of slag powder, adding 70-75 parts by weight of high density polyethylene, and stirring at high speed; (2) adding the above mixed materials into a screw pelletizer and pelleting; (3) putting the pelleted particles into a screw extruder and carrying out extrusion molding, carrying out vacuum setting, cooling, carrying out mechanical holing, and carrying out cutting forming; and (4) finally irradiating the packing bioreactor by short wave ultraviolet. According to the invention, hydrophily of the suspended packing bioreactor is greatly enhanced, surface adsorbing capacity is increased, biofilm adsorption strength is raised, biofilm culturing period is shortened, and the biofilm is not easy to fall off. The suspended packing bioreactor is suitable for processing low concentration organic wastewater and phenolic wastewater.