Ceftazidime is unstable to light and heat.The HPLC method for determining the related substances in ceftazidime was presented.The Spherisorb C18 column (200 mm X 4.6 mm, 5 μm) was used with acetonitrile - 0.04M NH4HPO4 (1:9, pH 7.0) as mobile phase; flow rate was 1 mL min-1, and detection wavelength was 254 nm.Ceftazidime, its degradation product (7-ACA), byproduct, and related substances were detected by the method.The stability of ceftazidime and its preparation was studied.The HPLC method was simple, rapid, accurate, and precise, which was better than that of foreign pharmacopeias.