The invention relates to the technical field of veterinary antibiotic synthesis, and particularly discloses a cephapirin sodium refining method. The cephapirin sodium refining method takes a cephapirin sodium crude product as a treatment object, and is characterized in that the cephapirin sodium crude product is dissolved in a dilute acid solution, activated carbon is added for decolorization, the filtrate is retained, and alkali liquor is slowly dropwise added to the filtrate, and then cooling, stirring and crystallizing are performed to obtain cephapirin acid; the cephapirin acid is washed, and then dissolved in a solvent containing dimethyl sulfoxide, the sodium salt is added into the cephapirin acid solution, and is stirred, cooled, and filtered to remove mother liquor to obtain a cephapirin sodium wet product, and the wet product is dried to obtain a product. The method of the invention has the characteristics of simple operation steps, high product purity, high yield, light color, cheap materials and low production cost, and can fully meet the requirements on the cephapirin sodium of European Pharmacopoeia.