A new indirect iodometric processes special for the determination of benzoyl per oxide was developed. This method is based on the oxidation of excess patassium iodide by benzoyl peroxide in the presence of citric acid as catalyst and masking agent, with acetone as solvent. The relative standard deviation is less than 0.28%. This method has the advantages of convenient operation, rapidity、reproducibilily and accuracy, the results are satisfactory.