Abstract: A spectrophotometric method has been developed for the determination of cefazolin sodium. It is based on the reaction of charge transfer with p-benzoquinone in pH 9.0 borax buffer solution.The maximum absorption of the complex is at 619.4 nm. The apparent molar absorptivity is 1.02×10⁴ L/(mol·cm) for p-benzoquinone. The calibration curves is linear within the concentration range of 0.9～48 μg/mL for p-benzoquinone. The complex composition of cefazolin sodium with p-benzoquinone is 1:2. The relative standard deviation is between 0.5%～5.3%. This proposed methods has been applied to the determination of cefazolin sodium in tablets with satisfactory results.