A method for the determination of sodium carbonate (as a cosolvent) in cephalosporin products using a HPLC method was developed. The chromatog. condition: the column was a silica gel with carboxylic groups particle (metrosep C4 7 μm × 100 mm × 4.0 mm). The mobile phase consisted of (1.7 mmol/L nitric acid + 0.7 mmol/L dipiconlinic acid)- acetonitrile (99:1), the detected was an elec. conductivity detector, the flow rate was 1.0 mL/min, the column temperature was 35°C, the sample size was 20 μL. As ceftazidime for injection for example, the calibration curve was linear (γ=1.0000) in the range of 4.9-14.7 μg/mL for sodium ion. The average recoveries were 100.9% (n=9), and the average RSD was 0.5%. The method is an accurate, simple, rapid, qual. method with good reproducibility for quality contract of sodium carbonate (as the complex solubilizer) in cephalosporin type antibiotics.