Objective: To develop a method to determine cefoperazone sodium in compound injection of cefoperazone sodium and tazobactam sodium by differentiated pulse voltammetry.Method: The different electrochemical behaviors of cefoperazone sodium was analyied by electrochemical analysis methods of cyclic voltammetry and differentiated pulse voltammetry to optimize the analytical method and conditions.Result: The tazobactam sodium in the compound injection had no response in the buffer solution of 250 mmol·L-1 sodium dihydrogen phosphate

cefoperazone sodium was in good linear relation with its peak current at a concentration range of 13.7-171.4 mg·L-1（r=0.999 4）;the lowest detectable limit was 2.58 mg·L-1 and the recovery rate was up to 97.8%-102.3%.Conclution: The method can eliminated the interference of tazobactam sodium for the determination of cefoperazone sodium.The content of cefoperazone sodium in compound injection could be determined by the method.The method has high sensitivity

less cost and reliable reproducibility.