Abstract: The main foreign steroids of commercially available prednisone acetate have been isolated by preparative HPLC and their IR spectra, mass spectra and NMR spectra are determined. From the results it was confirmed that the main foreign steroids are: 16-bromo-17, 21-dihydroxy (17α) pregna-1,4-diene-3, 11, 20-trione-21-acetate (Ⅱ), 11-deoxyprednisone acetate (Ⅱ) and cortisone acetate (Ⅲ).Ⅱ and Ⅲ were quantitatively determined by HPLC, using estradiol benzoate as an internal standard. At the same time, the linear relationship between the internal standard and 11-deoxyprednisone acetate or cortisone acetate was studied and was shown to be satisfactory.