Abstract: The microwave digestion/inductively coupled plasma method (ICP-OES) was used to determine 18 elemental impurities in flucloxacillin sodium for injection. The flucloxacillin sodium sample was digested with microwave after addition of concentrated nitric acid and determined with ICP-OES. The vertical observation mode was used to effectively reduce the interference of ionization effects for the easily ionized elements. The linear relationship of the proposed method was good and the coefficients were over 0.998. The limits of detection ranged from 0.000 1 to 0.032 1 mg/L. The relative standard deviations of repeatability and precision were less than 10%. The recoveries were in the range from 82.9% to 105.7%. Three batches of flucloxacillin sodium for injection were examined, and the contents of these elemental impurities in these samples met the requirements in ICH-Q3D and USP General Principle < 232>. This proposed method showed good sensitivity and precision, high accuracy and fast analysis speed, and would serve as a reliable method for quality control of flucloxacillin sodium for injection.