The invention discloses a preparing method of a hydrophobic PVDF ultrafiltration membrane. polyvinylidene fluoride is taken as the raw material of the membrane and is prepared by following steps: (1) according to parts by weight, adding 1-2 parts of polyvinylpyrrolidone and 1.9 parts of hydrogen peroxide, 2.3 parts of inorganic alkali solution into a reaction kettle, mixing uniformly, then adding 1.8 parts of dimethyl distearyl ammonium chloride, 17.4 parts of dichlorofluoroethane solvent and 1.7 parts of isobutyryl chloride solution, and stirring for reacting at -6.5 DEG C for 38min; (2) then, according to parts by weight, adding 2.2 parts of fatty alcohol ether sodium sulfate, 4.2 parts of sodium polyacrylate solution and 73 parts of vinylidene fluoride monomer, 4.3 parts of 1,2,3-trimethylcyclopentane, stirring for reacting at 11 DEG C, and terminating the reacting when pressure drops to be below 0.18MPa; (3) filtering, washing and drying to obtain powdery polyvinylidene fluoride. The hydrophobic PVDF ultrafiltration membrane has anticorrosive, heat resistant, cold resistant, antioxidant and weather resistant performances.