NOVELTY - Preparing prednisone involves subjecting 11 alpha -hydroxy-16,17a-epoxyprogesterone (i) to Platt's oxidation using chromic acid and glacial acetic acid to form Platt's substance (i.e. corresponding 11-oxo-dienone compound (ii)); followed by bromination of (ii) to form bromohydrin; that is subjected to debromination; iodination at 21 position followed by replacing iodo group with hydroxyl to form prednisone.    USE - For preparing prednisone that is used as anti-inflammatory and antiallergic medicine.    ADVANTAGE - The present method for producing prednisone is improved as compared to the prior methods (that results in large amount of chromium waste and waste of acetic acid). In the present method, the chromium containing wastewater after Platt's oxidation can be applied repeatedly and this reduces the cost of the acetic acid recovery. As the reaction involves an all confined treatment, wastewater after treatment is discharged after full recovery of chromium thus reducing pollution. Also the chromium-containing wastewater treatment method is simple, satisfying chromium quality standards, with no adverse effect on the reaction.    DETAILED DESCRIPTION - Preparing prednisone involves subjecting 11 alpha -hydroxy-16,17a-epoxyprogesterone (i) to Platt's oxidation to form Platt's substance of formula (ii); followed by bromination of (ii) to form bromohydrin of formula (iii); that is subjected to debromination; iodination at 21 position followed by replacing iodo group with hydroxyl to form prednisone. The platt's oxidation involves pumping certain amount of glacial acetic acid into a reaction kettle, stirring, adding 100-500 wt.% of (i); dissolving for about 15-60 minutes, cooling to 0-10 degrees C, dipping chromic acid solution for 1-1.5 h, controlling temperature at 8-15 degrees C, slowly heating to 25 degrees C, controlling the temperature of the whole process at 24-26 degrees C, keeping temperature for 5-6 h, drawing the reaction liquid into a crystal extracting kettle after keeping temperature, adding water, extracting crystal under stirring, centrifuging after 15-30 minutes, washing by suitable amount of water, drying, recycling mother liquor and drying the solid material into a drying chamber to obtain (ii).