The invention discloses a purification method of cefazolin acid, and belongs to the technical field of medicines. The purification method of the cefazolin acid comprises the following steps: A, addingraw materials into purified water, controlling the temperature, adding alkali liquor to adjust the pH of a system, and stirring until the solution is clear; B, adding an organic solvent and stirring,standing for phase separation, and retaining a water phase; C, adding acetone and a buffer solution into the water phase, controlling the temperature, dropwise adding an acid solution to regulate thepH value of the system, adding a seed crystal, and carrying out primary crystal growing; D, adding purified water, dropwise adding an acid solution to adjust pH, cooling and secondarily growing crystals; and E, filtering to obtain a filter cake, washing the filter cake at first, drying the filter cake under vacuum and discharging to obtain the purified cefazolin acid. The purified cefazolin acidobtained by the purification method not only meets the requirement of preparation of the cefazolin acid by a subsequent freeze-drying method, but also can be applied to preparation of high-content cefazolin acid standard substances.