The invention discloses a method for preparing cefoperazone sodium. The method comprises steps as follows: dissolving: acetone and purified water are added to a reaction tank, stirring is started, cefoperazone acid is added, pH (potential of hydrogen) is adjusted to be 6.8-7.2, and cefoperazone acid is completely dissolved; decoloration: activated carbon is added to a cefoperazone acid solution for decoloration, and the cefoperazone acid solution is pressed into a crystallizing tank of a sterilizing room through a decarbonization filter and a multilevel bacterium removal filter element; crystallization: an organic solvent is fed to the crystallizing tank for crystallization; crystals grow under the stirring condition, a three-in-one filter is used for filtration, and a filter cake is washed with acetone; drying: the washed filter cake enters a drying device, sterilized and filtered methanol, water or methanol water is atomized through a direct-injection type atomization device, atomized steam is driven by sterile nitrogen to blow the filter cake for 2 h plus or minus 1.5 h, then, hot water is provided for circulation heating, the filter cake is dried in a vacuum state until residual solvents are qualified, and then cefoperazone sodium is discharged. The acetone residues in a cefoperazone sodium product are far smaller than 0.5%, the product quality and the stability are improved, medication is safer, and good social benefits are generated.