The invention discloses a preparation method of a polyvinylidene fluoride ultrafiltration membrane. Polyvinylidene fluoride is taken as a raw material of the membrane and is prepared by the following steps: (1) putting 1 to 2 parts by weight of sodium tripolyphosphate, 2.3 parts by weight of hydrogen peroxide, 1.4 parts by weight of inorganic aqueous alkali into a reaction still, uniformly mixing, then putting 1.4 parts by weight of benzoyl peroxide, 11.3 parts by weight of 1,1,2-trichlorotrifluoroethane solvent, and 0.2 part by weight of perfluoro butanesulfonylfluoride solution in, and stirring at the temperature of 8 DEG C below zero for reacting for 30 minutes; (2) then putting 0.9 part by weight of lauroyl aminoethyl sodium sulfate, 5.7 parts by weight of polypropylene glycol solution, 62 parts by weight of polyvinyl fluoride monomer and 2.5 parts by weight of dibromo-cyclopentane in, stirring at the temperature of 25 DEG C for the reaction, and finishing the reaction when the pressure is reduced to be below 0.21MPa; (3) filtering, washing and drying to obtain the powdery polyvinylidene fluoride. The membrane prepared by the preparation method has corrosion resistance, heat resistance, cold resistance, oxidation resistance and weather resistance.